A student is trying to decide what to wear.His bedroom is at 20.0 °C.His skin temperature is 35.0 °C.The area of his exposed skin is 1.50 m².People all over the world have skin that is dark in the infrared,with emissivity about 0.900.Find the net energy transfer from his body by radiation in 10.0 min.

Answers

Answer 1

Answer:

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Related Questions

Two long, parallel, current-carrying wires lie in an xy-plane. The first wire lies on the line y = 0.300 m and carries a current of 26.0 A in the +x direction. The second wire lies along the x-axis. The wires exert attractive forces on each other, and the force per unit length on each wire is 295 µN/m. What is the y-value (in m) of the line in the xy-plane where the total magnetic field is zero?

Answers

Answer:

The y-value  is  z = 0.759 m

Explanation:

From the question we are told that

     The position of the first y-axis is  [tex]y_1 = 0.300 \ m[/tex]

     The current on the first wire is  [tex]I_ 1 = 26.0 \ A[/tex]

      The force per unit length on each wire is  [tex]\frac{F}{l} = 295 \mu N/m = 295 * 10^{-6} \ N/m[/tex]

Generally the force per unit length on first wire is mathematically represented as

                [tex]\frac{F}{l} = \frac{\mu_o * I_1 * I_2 }{2*\pi* y_1}[/tex]

Where  [tex]\mu _o[/tex] is the permeability of free space with value  [tex]\mu_o = 4\pi * 10^{-7} N/A^2[/tex]

    substituting values

                    [tex]295 *10^{-6} = \frac{ 4\pi * 10^{-7} * 26.0 * I_2 }{2 *3.142* 0.300}[/tex]

                [tex]I_2 = \frac{295 *10^{-6 } * 0.300 * 2* 3.142 }{ 4\pi * 10^{-7} * 26 }[/tex]

                 [tex]I_2 = 17.0 \ A[/tex]

Now the at the point where the magnetic field is zero the magnetic field of each wire are equal , let that point by z meters from the second wire on the y-axis  so

             [tex]\frac{\mu_o I_2}{2 * \pi * y_1} = \frac{\mu_o I_1}{2 * \pi * (y_1-z)}[/tex]

          [tex]I_2 (y_1 - z) = I_1 * y_1[/tex]

substituting values

         [tex]17.0 ( 0.300 - z) = 26 * 0.300[/tex]

         z = 0.759 m

Visible light of wavelength 589 nm is incident on a diffraction grating that has 3500 lines/cm. At what angle with respect to the central maximum is the fifth order maximum observed

Answers

Answer:

dsinФ=mΔ

d=1/N

d=1/3500*[tex]10^{-2} m\\[/tex]

d=2.8*[tex]10^{-6}[/tex]

NOw apply all values on formula

dsinФ=mΔ

2.8*[tex]10^{-6\\}[/tex]sinФ=5*589*[tex]10^{-9}[/tex]

sinФ=1.05 error

so due fifth maximum order it cannot be soved by this grating

An electron moves in a circular path perpendicular to a uniform magnetic field with a magnitude of 2.14 mT. If the speed of the electron is 1.48 107 m/s, determine the following.
(a) the radius of the circular path ............ cm
(b) the time interval required to complete one revolution ............ s

Answers

Answer:

(a) 3.9cm

(b) 1.66 x 10⁻⁸s

Explanation:

Since the electron is moving in a circular path, the centripetal acceleration needed to keep it from slipping off is provided by the magnetic force. This force (F), according to Newton's second law of motion is given by,

F = m x a          --------------(i)

Where;

m = mass of the particle

a = acceleration of the mass

The centripetal acceleration is given by;

a = v² / r          [v = linear velocity of particle, r = radius of circular path]

Therefore, equation (i) becomes;

F = m v²/ r             --------------------(ii)

The magnitude of the magnetic force on a moving charge in a magnetic field as stated by Lorentz's law is given by;

F = qvBsinθ          -------------(iii)

Where;

q = charge of the particle

v = velocity of the particle

B = magnetic field

θ = angle between the velocity and the magnetic field

Combine equations (ii) and (iii) as follows;

m (v² / r) = qvBsinθ         [divide both side by v]

m v / r = qBsinθ              [make r subject of the formula]

r = (m v) / (qBsinθ)              ---------(iv)

(a) From the question;

v = 1.48 x 10⁷m/s

B = 2.14mT = 2.14 x 10⁻³T

θ = 90°          [since the direction of velocity is perpendicular to magnetic field]

m = mass of electron = 9.11 x 10⁻³¹kg

q = charge of electron = 1.6 x 10⁻¹⁹C

Substitute these values into equation (iv) as follows;

r = (9.11 x 10⁻³¹ x 1.48 x 10⁷) / (1.6 x 10⁻¹⁹ x 2.14 x 10⁻³ sin 90°)

r = 3.9 x 10⁻²m

r = 3.9cm

Therefore, the radius of the circular path is 3.9cm

(b) The time interval required to complete one revolution is the period (T) of the motion of the electron and it is given by

T = d / v          --------------(*)

Where;

d = distance traveled in the circular path in one complete turn = 2πr

v = velocity of the motion = 1.48 x 10⁷m/s

d = 2 π (3.9 x 10⁻²)            [Take π = 22/7 = 3.142]

d = 2(3.142)(3.9 x 10⁻²) = 0.245m

Substitute the values of d and v into equation (*) as follows;

T = 0.245 / 1.48 x 10⁷

T = 0.166 x 10⁻⁷s

T = 1.66 x 10⁻⁸s

Therefore, the time interval is 1.66 x 10⁻⁸s

Three identical capacitors are connected in series to a battery. If a total charge of Q flows from the battery, how much charge does each capacitor carry?

Answers

Answer:

Each of the capacitor carries the same charge, Q

Explanation:

When capacitors are connected in series, the battery voltage is divided equally across the capacitors. The total voltage across the three identical capacitors is calculated as follows;

[tex]V_T = V_1 + V_2 + V_3[/tex]

We can also calculate this voltage in terms of capacitance and charge;

[tex]V = \frac{Q}{C} \\\\V_T = V_1 + V_2 +V_3 \\\\(given \ total \ charge \ as \ Q, then \ the \ total \ voltage \ V_T \ can \ be \ written \ as)\\\\V_T = \frac{Q}{C_1} + \frac{Q}{C_2} + \frac{Q}{C_3} \\\\V_T = Q(\frac{1}{C_1 } +\frac{1}{C_2} + \frac{1}{C_3 })\\\\[/tex]

Therefore, each of the capacitor carries the same charge, Q

What is the length of the x-component of the vector shown below?
9
380
х
A. 5.5
B. 30.0
O O
O C. 7.1
O D. 8.6

Answers

Answer:

x-component = 7.1

Explanation:

x-component = 9cos38 = 7.09 =7.1

Answer:

7.1

Explanation:

use cos

Suppose a 185 kg motorcycle is heading toward a hill at a speed of 29 m/s. The two wheels weigh 12 kg each and are each annular rings with an inner radius of 0.280 m and an outer radius of 0.330 m.
Randomized Variables
m = 185 kg
v = 29 m/s
h = 32 m
A. How high can it coast up the hill. if you neglect friction in m?
B. How much energy is lost to friction if the motorcycle only gains an altitude of 33 m before coming to rest?

Answers

Answer:

a) Height reached before coming to rest is 42.86 m

b) Energy lost to friction is 17902.45 J

Explanation:

mass of the motorcycle = 185 kg

speed of the towards the hill = 29 m/s

The wheels weigh 12 kg each

Wheels are annular rings with an inner radius of 0.280 m and outer radius of 0.330 m

a) To go up the hill, the kinetic energy of motion of the motorcycle will be converted to the potential energy it will gain in going up a given height

the kinetic energy of the motorcycle is given as

[tex]KE[/tex] = [tex]\frac{1}{2}mv^{2}[/tex]

where m is the mass of the motorcycle

v is the velocity of the motorcycle

[tex]KE[/tex]  = [tex]\frac{1}{2}*185*29^{2}[/tex] = 77792.5 J

This will be converted to potential energy

The potential energy up the hill will be

[tex]PE[/tex] = mgh

where m is the mass

g is acceleration due to gravity 9.81 m/s^2

h is the height reached before coming to rest

[tex]PE[/tex] = 185 x 9.81 x m = 1814.85h

equating the  kinetic energy to the potential energy for energy conservation, we'll have

77792.5 = 1814.85h

height reached before coming to rest  = 77792.5/1814.85 = 42.86 m

b) if an altitude of 33 m was reached before coming to rest, then the potential energy at this height is

[tex]PE[/tex] = mgh

[tex]PE[/tex]  = 185 x 9.81 x 33 = 59890.05 J

The energy lost to friction will be the kinetic energy minus this potential energy.

energy lost = 77792.5 - 59890.05 = 17902.45 J

A) The motorcycle can coast up the hill by ; 42.86m  

B) The amount of energy lost to friction :  17902.45 J

A) Determine how high the motorcycle can coast up the hill when friction is neglected

apply the formula for kinetic and potential energies

K.E = 1/2 mv²  ---- ( 1 )

P.E = mgH  ---- ( 2 )

As the motorcycle goes uphiLl the kinetic energy is converted to potential energy.

∴ K.E = P.E

1/2 * mv² = mgH

∴ H = ( 1/2 * mv² ) / mg  ---- ( 3 )

where ; m = 185 kg ,  v = 29 m/s ,  g = 9.81

Insert values into equation ( 3 )

H ( height travelled by motorcycle neglecting friction ) =  42.86m  

B) Determine how much energy is lost to friction if the motorcycle attains 33m before coming to rest  

P.E = mgh = 185 * 9.81 * 33  = 59890.05 J

where : h = 33 m , g = 9.81

K.E = 1/2 * mv² = 77792.5 J   ( question A )

∴ Energy lost ( ΔE ) =  ( 77792.5  - 59890.05 ) = 17902.45 J

Hence we can conclude that The motorcycle can coast up the hill by ; 42.86m , The amount of energy lost to friction :  17902.45 J.

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BIO A trap-jaw ant snaps its mandibles shut at very high speed, a good trait for catching small prey. But an ant can also slam its mandibles into the ground; the resulting force can launch the ant into the air for a quick escape. A 12 mg ant hits the ground with an average force of 47 mN for a time of 0.13 ms; these are all typical values. At what speed does it leave the ground

Answers

Answer:

Final velocity (v) = 0.509 m/s (Approx)

Explanation:

Ant use impulse power

Given:

Mass of ant = 12 mg = 12 × 10⁻⁶ kg

Average force = 47 mN = 47 × 10⁻³ N

Initial velocity(u) = 0

Time taken = 0.13 ms = 0.13 × 10⁻³ s

Find:

Final velocity (v)

Computation:

Force × Time =  change in momentum

(47 × 10⁻³ N)(0.13 × 10⁻³ s) = mv - mu

(47 × 10⁻³ N)(0.13 × 10⁻³ s) = m(v - u)

6.11 × 10⁻⁶ = 12 × 10⁻⁶(v - 0)

6.11 = 12 v

Final velocity (v) = 0.509 m/s (Approx)

Someone help find centripetal acceleration plus centripetal force!

Answers

Answer:Centripetal force that acts an object keep it along a moving circular path.

Explanation:Centripetal force along a path circular of radius(r) with velocity(V) acceleration the center of the path.

a=v/r

object will along moving continue a straight path unless by the external force.External force is the centripetal force.

Centripetal force is to moving in horizontal circle,Centripetal force is not a fundamental force.Gravitational force satellite and orbit of centripetal force.

Centripetal acceleration and centripetal force are used to calculate the motion of objects in circular motion. The main answer to the question is given below:The centripetal force is given by:F = mv²/rwhere m is the mass of the object, v is the speed of the object and r is the radius of the circle. The unit of centripetal force is Newtons (N).The centripetal acceleration is given by:a = v²/rThe unit of centripetal acceleration is meters per second squared

(m/s²).Explanation:When an object moves in a circular motion, there is a force that acts upon it. This force is called the centripetal force. This force always points towards the center of the circle. It is responsible for keeping the object moving in a circular motion.The centripetal force is related to the centripetal acceleration.

The centripetal acceleration is the acceleration of an object moving in a circle. It is always directed towards the center of the circle.The magnitude of the centripetal force is given by:F = mv²/rwhere F is the force, m is the mass of the object, v is the speed of the object and r is the radius of the circle.The magnitude of the centripetal acceleration is given by:a = v²/rwhere a is the acceleration, v is the speed of the object and r is the radius of the circle.

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Uses of pressure and the uses of density​

Answers

Answer:

Pressure is  a scalar quantity defined as per unit area.

Density is the objects ,times its  the acceleration due to gravity.

Explanation:

Pressure is the alternative object increases the area of contact decrease .

Pressure is the force component  to the surface used to calculate pressure.

pressure is that collisions of the gas to container as the per unit time .

pressure is an physical important quantity to play the solid and  fluid .

Pressure is the expressed in a number of units depend the context use, pressure exerted by the liquid alone.

Density is the  objects, times, volume of the object that times acceleration objects.

Density is the used to the system complex objects and materials.

Density  force is the weight of a region or objects static fluid.

The electron beam inside a television picture tube is 0.40 {\rm mm} in diameter and carries a current of 50 {\rm \mu A}. This electron beam impinges on the inside of the picture tube screen.
How many electrons strike the screen each second?
The electrons move with a velocity of 4.0\times10^7\;{\rm m/s}. What electric field strength is needed to accelerate electrons from rest to this velocity in a distance of 5.0 {\rm mm}?
Each electron transfers its kinetic energy to the picture tube screen upon impact. What is the power delivered to the screen by the electron beam? (Hint: What potential difference produced the field that accelerated electrons? This is an emf.)

Answers

Answer:

A.3.13x10^14 electrons

B.330A/m²

C.9.11x10^5N/C

D. 0.23W

.pls see attached file for explanations

A person is nearsighted with a far point of 75.0 cm. a. What focal length contact lens is needed to give him normal vision

Answers

Complete Question

The  complete question is  shown on the first uploaded image  

Answer:

a

  [tex]f= -75 \ cm = - 0.75 \ m[/tex]

b

  [tex]P = -1.33 \ diopters[/tex]

Explanation:

From the question we are told that

    The  image distance is  [tex]d_i = -75 cm[/tex]

The value of the image is negative because it is on the same side with the corrective glasses

    The  object distance is  [tex]d_o = \infty[/tex]

The  reason object distance  is because the object father than it being picture by the eye

General focal length is mathematically represented as

              [tex]\frac{1}{f} = \frac{1}{d_i} - \frac{1}{d_o}[/tex]

substituting values

             [tex]\frac{1}{f} = \frac{1}{-75} - \frac{1}{\infty}[/tex]

=>         [tex]f= -75 \ cm = - 0.75 \ m[/tex]

Generally the power of the corrective lens is  mathematically represented as

        [tex]P = \frac{1}{f}[/tex]

substituting values

       [tex]P = \frac{1}{-0.75}[/tex]

        [tex]P = -1.33 \ diopters[/tex]

A parallel-plate capacitor in air has circular plates of radius 2.8 cm separated by 1.1 mm. Charge is flowing onto the upper plate and off the lower plate at a rate of 5 A. Find the time rate of change of the electric field between the plates.

Answers

Answer:

The time rate of change of the electric field between the plates is  [tex]\frac{E }{t} = 2.29 *10^{14} \ N \cdot C \cdot s^{-1}[/tex]  

Explanation:

From the question we are told that

    The  radius is  [tex]r = 2.8 \ cm = 0.028 \ m[/tex]

     The distance of separation is  [tex]d = 1.1 \ mm = 0.0011 \ m[/tex]

      The  current is  [tex]I = 5 \ A[/tex]

Generally the electric field generated is mathematically represented as

         [tex]E = \frac{q }{ \pi * r^2 \epsilon_o }[/tex]

Where [tex]\epsilon_o[/tex] is the permitivity of free space with a value

          [tex]\epsilon_o = 8.85*10^{-12 }\ m^{-3} \cdot kg^{-1}\cdot s^4 \cdot A^2[/tex]

So the time rate of change of the electric field between the plates is mathematically represented as

        [tex]\frac{E }{t} = \frac{q}{t} * \frac{1 }{ \pi * r^2 \epsilon_o }[/tex]

But [tex]\frac{q}{t } = I[/tex]

So  

       [tex]\frac{E }{t} = * \frac{I }{ \pi * r^2 \epsilon_o }[/tex]

substituting values  

        [tex]\frac{E }{t} = * \frac{5 }{3.142 * (0.028)^2 * 8.85 *10^{-12} }[/tex]

        [tex]\frac{E }{t} = 2.29 *10^{14} \ N \cdot C \cdot s^{-1}[/tex]

An electron moves in a circular path perpendicular to a magnetic field of magnitude 0.285 T. If the kinetic energy of the electron is 2.10 10-19 J, find the speed of the electron and the radius of the circular path. (a) the speed of the electron

Answers

Answer:

The speed of the electron is 6.79 x 10⁵ m/s

The radius of the circular path is 1.357 x 10⁻⁵ m

Explanation:

Given;

magnetic field, B = 0.285 T

energy of electron, E = 2.10 x 10⁻¹⁹ J

The kinetic energy of the electron is calculated as;

[tex]K.E = \frac{1}{2} m_eV^2[/tex]

Where;

[tex]m_e[/tex] is the mass of electron = 9.11 x 10⁻³¹ kg

V is the speed of the electron

[tex]K.E = \frac{1}{2} m_eV^2\\\\V^2 = \frac{2.K.E}{m_e} \\\\V = \sqrt{\frac{2K.E}{m_e} } \\\\V = \sqrt{\frac{2*(2.1*10^{-19})}{9.11*10^{-31}} }\\\\V = 6.79 *10^{5} \ m/s[/tex]

The radius of the circular path is given by;

[tex]R = \frac{M_eV}{qB}[/tex]

where;

q is the charge of the electron = 1.6 x 10⁻¹⁹ C

[tex]R = \frac{M_eV}{qB} \\\\R = \frac{9.11 *10^{-31}*6.79 *10^{5}}{1.6*10^{-19}*0.285} \\\\R = 1.357 *10^{-5} \ m[/tex]

A toboggan is sliding down an icy slope. As it goes down, _________ does work on the toboggan and ends up converting __________ energy to _________ energy.

Answers

Answer:

As it goes down, weight does work on the toboggan and it ends up converting gravitational potential energy to kinetic energy.

1. weight

2. gravitational potential energy to kinetic energy.

Explanation:

As it goes down, weight does work on the toboggan and it ends up converting gravitational potential energy to kinetic energy.

work done by toboggan = weight × distance

W = mg and the distance is down the icy slope

By using law of conservation of energy, energy can neither be created nor destroyed, but can be conserve from one form to another in a closed system.

Toboggan converts gravitational potential energy (mgh) to kinetic energy(¹/₂mv²)

A scooter is traveling at a constant speed v when it encounters a circular hill of radius r = 480 m. The driver and scooter together have mass m = 159 kg.
(a) What speed in m/s does the scooter have if the driver feels weightlessness (i.e., has an apparent weight of zero) at the top of the hill?
(b) If the driver is traveling at the speed above and encounters a hill with a radius 2r,

Answers

Answer:

68.585m/sec , 779.1 N

Explanation:

To feel weightless, centripetal acceleration must equal g (9.8m/sec^2). The accelerations then cancel.

From centripetal motion.

F =( mv^2)/2

But since we are dealing with weightlessness

r = 480m

g = 9.8m/s^2

M also cancels, so forget M.

V^2 = Fr

V = √ Fr

V =√ (9.8 x 480) = 4704

= 68.585m/sec.

b) Centripetal acceleration = (v^2/2r) = (68.585^2/960) = 4704/960

= 4.9m/sec^2.

Weight (force) = (mass x acceleration) = 159kg x (g - 4.9)

159kg × ( 9.8-4.9)

159kg × 4.9

= 779.1N

A) The speed of the scooter at which the driver will feel weightlessness is;

v = 68.586 m/s

B) The apparent weight of both the driver and the scooter at the top of the hill is;

F_net = 779.1 N

We are given;

Mass; m = 159 kg

Radius; r = 480 m

A) Since it's motion about a circular hill, it means we are dealing with centripetal force.

Formula for centripetal force is given as;

F = mv²/r

Now, we want to find the speed of the scooter if the driver feels weightlessness.

This means that the centripetal force would be equal to the gravitational force.

Thus;

mg = mv²/r

m will cancel out to give;

v²/r = g

v² = gr

v = √(gr)

v = √(9.8 × 480)

v = √4704

v = 68.586 m/s

B) Now, he is travelling with speed of;

v = 68.586 m/s

And the radius is 2r

Let's first find the centripetal acceleration from the formula; α = v²/r

Thus; α = 4704/(2 × 480)

α = 4.9 m/s²

Now, since he has encountered a hill with a radius of 2r up the slope, it means that the apparent weight will now be;

F_app = m(g - α)

F_net = 159(9.8 - 4.9)

F_net = 779.1 N

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which of the following is true about scientific models?
A. models are used to simplify the study of things
B.computer models are the most reliable kind of model
C. models explain past, present and future information
D.a model is accurate if it does not change over time

Answers

A) used to simplify the study of things

Answer:

A- to simplify the study of things

Explanation:

a visual reference

The temperature gradient between the core of Mars and its surface is approximately 0.0003 K/m. Compare this temperature gradient to that of Earth. What can you determine about the rate at which heat moves out of Mars’s core compared to Earth?

Answers

Answer:

The temperature gradient between the core of Mars and its surface is lower than that on Earth. So, heat moves outward more slowly on Mars than on Earth.

Explanation:

Answer:

The temperature gradient between the core of Mars and its surface is lower than that on Earth. So, heat moves outward more slowly on Mars than on Earth.

Explanation:

Edmentum sample answer

How much heat is needed to melt 2.5 KG of water at its melting point? Use Q= mass x latent heat of fusion.

Answers

Answer:

Q = 832 kJ

Explanation:

It is given that,

Mass of the water, m = 2.5 kg

The latent heat of fusion, L = 333 kJ/kg

We need to find the heat needed to melt water at its melting point. The formula of heat needed to melt is given by :

Q = mL

[tex]Q=2.5\ kg\times 333\ kJ/kg\\\\Q=832.5\ kJ[/tex]

or

Q = 832 kJ

So, the heat needed to melt the water is 832 kJ.

Before you start taking measurements though, we’ll first make sure you understand the underlying concepts involved. By what method is each of the spheres charged?

Answers

Answer:

If they are metallic spheres  they are connected to earth and a charged body approaches

non- metallic (insulating) spheres in this case are charged by rubbing

Explanation:

For fillers, there are two fundamental methods, depending on the type of material.

If they are metallic spheres, they are connected to earth and a charged body approaches, this induces a charge of opposite sign and of equal magnitude, then it removes the contact to earth and the sphere is charged.

If the non- metallic (insulating) spheres in this case are charged by rubbing with some material or touching with another charged material, in this case the sphere takes half the charge and when separated each sphere has half the charge and with equal sign.

1. Notice that the voltmeter moves in response to the coil entering or leaving the magnetic gap.
2. Let's apply Faraday's Law to this situation. Faraday's Law says that the induced voltage (or emf )in a loop of wire caused by a changing magnetic field is:
€ = 1
Where is the magnetic flux which is
Q = BA
In this case, the flux density B is not changing. Instead, the changing flux is due to the motion of the coil as it enters or leaves the magnetic gap:
do = BdA
Given that the area immersed in the gap is changing as the coil enters the gap, what is the correct expression of Faraday's Law for this situation?

Answers

Answer:

Explanation:

let the coil of length l and breathe b entering the magnetic field B with speed v.

So, the magnetic flux through the coil is

Ф = B(l×b)

length × breathe = area

Ф = BA

dФ = BdA

therefore induced emf is given as

ε = [tex]Bl(\frac{db}{dt})[/tex]

note: [tex]\frac{db}{dt} = v[/tex]

ε[tex]= Blv[/tex]

attached is the diagram for the solution

Which is true about a concave mirror? Incident rays that are parallel to the central axis are dispersed but will be perceived as originating from a point on the near side of the mirror.

Answers

Answer:

'Incident rays that are parallel to the central axis are sent through a point on the near side of the mirror'.

Explanation:

The question is incomplete, find the complete question in the comment section.

Concave mirrors is an example of a curved mirror. The outer surface of a concave mirror is always coated. On the concave mirror, we have what is called the central axis or principal axis which is a line cutting through the center of the mirror. The points located on this axis are the Pole, the principal focus and the centre of curvature. The focus point is close to the curved  mirror than the centre of curvature.

During the formation of images, one of the incident rays (rays striking the plane surface) coming from the object and parallel to the principal axis, converges at the focus point after reflection because all incident rays striking the surface are meant to reflect out. All incident light striking the surface all converges at a point on the central axis known as the focus.

Based on the explanation above, it can be concluded that 'Incident rays that are parallel to the central axis are sent through a point on the near side of the mirror'.

A spherical shell has inner radius 1.5 m, outer radius 2.5 m, and mass 850 kg, distributed uniformly throughout the shell. What is the magnitude of the gravitational force exerted on the shell by a point mass particle of mass 2.0 kg a distance 1.0 m from the center

Answers

Answer:

The magnitude of the gravitational force is 4.53 * 10 ^-7 N

Explanation:

Given that the magnitude of the gravitational force is F = GMm/r²

mass M = 850 kg

mass m = 2.0 kg

distance d = 1.0 m , r = 0.5 m

F = GMm/r²

Gravitational Constant G = 6.67 × 10^-11 Newtons kg-2 m2.

F = (6.67 × 10^-11 * 850 * 2)/0.5²

F = 0.00000045356 N

F = 4.53 * 10 ^-7 N

An MRI machine needs to detect signals that oscillate at very high frequencies. It does so with an LC circuit containing a 15mH coil. To what value should the capacitance be set to detect a 450 MHz signal?

Answers

Answer:

The capacitance is  [tex]C = 3.2 9 *10^{-16} \ F[/tex]

Explanation:

From the question we are told that

   The  induction of the LC circuit is  [tex]L = 15 mH = 15 *10^{-3} \ H[/tex]

    The  frequency is   [tex]w = 450 \ MHz = 450 *10^{6} \ Hz[/tex]

The natural frequency is mathematically represented as

          [tex]w = \frac{1}{\sqrt{LC} }[/tex]

Where C is the capacitance So  

=>      [tex]C = \frac{1}{L * w^2}[/tex]

substituting values

         [tex]C = \frac{1}{15 *10^{-3} * [450 *10^{6}]^2}[/tex]

         [tex]C = 3.2 9 *10^{-16} \ F[/tex]

The value for which the capacitance should be set to detect a 450 MHz signal is [tex]8.34 \times 10^{-24} \;F[/tex]

Given the following data:

Inductance = 15 mH = [tex]15 \times 10^{-3}\;H[/tex]Frequency = 450 MHz = [tex]450 \times 10^6 \;Hz[/tex]

To determine the value for which the capacitance should be set to detect a 450 MHz signal:

Mathematically, natural frequency is given by the formula:

[tex]f_o = \frac{1}{2\pi \sqrt{LC} }[/tex]

Where:

L is the inductance.C is the capacitance.

Making C the subject of formula, we have:

[tex]C = \frac{1}{(2\pi f_o)^2L} \\\\C = \frac{1}{(2\;\times \;3.142 \times \;450 \;\times\; 10^9)^2 \; \times \;15 \times 10^{-3}}\\\\C = \frac{1}{8 \times 10^{24} \;\times \;15 \times 10^{-3} } \\\\C = \frac{1}{1.2 \times 10^{23}} \\\\C= 8.34 \times 10^{-24} \;F[/tex]

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Suppose you have two point charges of opposite sign. As you move them farther and farther apart, the potential energy of this system relative to infinity:_____________.
(a) stays the same.
(b) Increases.
(c) Decreases.
(d) The answer would depend on the path of motion

Answers

Answer:

(b) Increases

Explanation:

The potential energy between two point charges is given as;

[tex]U = F*r = \frac{kq_1q_2}{r}[/tex]

Where;

k is the coulomb's constant

q₁  ans q₂ are the two point charges

r is the distance between the two point charges

Since the two charges have opposite sign;

let q₁ be negative and q₂ be positive

Substitute in these charges we will have

[tex]U = \frac{k(-q_1)(q_2)}{r} \\\\U = - \frac{kq_1q_2}{r}[/tex]

The negative sign in the above equation shows that as the distance between the two charges increases, the potential energy increases as well.

Therefore, as you move the point charges farther and farther apart, the potential energy of this system relative to infinity Increases.

7.00 kg piece of solid copper metal at an initial temperature T is placed with 2.00 kg of ice that is initially at -20.0°C. The ice is in an insulated container of negligible mass and no heat is exchanged with the surroundings. After thermal equilibrium is reached, there is 0.90 kg of ice and 1.10 kg of liquid water.

Required:
What was the initial temperature of the piece of copper?

Answers

Answer:

122°C

Explanation:

From the data Final temperature is 0 deg C since there is 0.9kg of ice and 1.10kg of liquid water.

That means that 1.10kg of the ice undergoes Heat of Fusion which is 3.34x10^5 J/kg...

Heat lost by copper = Heat gained by ice + Heat of fusion

-> (7.0kg)(390J/kg*C)(0-T) = (2.00kg)(2100J/kg*C)(0 - (-20) + (1.10kg)(3.34x10^5 J/kg)

-> T(2730) = 334001

-> T = 122°C

A plane is flying horizontally with a constant speed of 55 .0 m/s when it drops a
rescue capsule. The capsule lands on the ground 12.0 s later.

c) How would your answer to part b) iii change if the constant speed of the plane is
increased? Explain.​

Answers

Answer:

therefore horizontal displacement changes increasing with linear velocity

Explanation:

Since the plane flies horizontally, the only speed that exists is

              v₀ₓ = 55.0 m / s

the time is the time it takes to reach the floor, which we can find because the speed on the vertical axis is zero

               y =y₀ + v₀ t - ½ g t2

               0 = I₀ + 0 - ½ g t2

               t = √ 2y₀o / g

time is that we use to calculate the x-axis displacement

 The distance it travels to reach the floor is

              x = v t

              x = 55 12

              x = 660 m

When the speed horizontally the time remains the same and 120

             x ’= v’ 12

therefore horizontal displacement changes increasing with linear velocity

A person with normal vision can focus on objects as close as a few centimeters from the eye up to objects infinitely far away. There exist, however, certain conditions under which the range of vision is not so extended. For example, a nearsighted person cannot focus on objects farther than a certain point (the far point), while a farsighted person cannot focus on objects closer than a certain point (the near point). Note that even though the presence of a near point is common to everyone, a farsighted person has a near point that is much farther from the eye than the near point of a person with normal vision.

Both nearsightedness and farsightedness can be corrected with the use of glasses or contact lenses. In this case, the eye converges the light coming from the image formed by the corrective lens rather than from the object itself.

Required:
a. If a nearsighted person has a far point df that is 3.50 m from the eye, what is the focal length f1 of the contact lenses that the person would need to see an object at infinity clearly?
b. If a farsighted person has a near point that is 0.600 m from the eye, what is the focal length f2 of the contact lenses that the person would need to be able to read a book held at 0.350 m from the person's eyes?

Answers

Answer:

a)   f₁ = 3.50 m ,  b)     f₂ = 0.84 m  

Explanation:

For this exercise we must use the constructor equation

          1 / f = 1 / p + 1 / q

where f is the focal length, p is the distance to the object and q is the distance to the image

a) the distance where the image should be placed is q = 3.50 m and the object is located at infinity p = ∞

           1 / f₁ = 1 /∞ + 1 / 3.50

           f₁ = 3.50 m

b) in this case the image is at q = -0.600 m and the object p = 0.350 m

           1 / f₂ = 1 / 0.350 -1 / 0.600

the negative sign, is because the image is in front of the object

           1 / f₂ = 1,1905

            f₂ = 1 / 1,1905

            f₂ = 0.84 m

the efficiency of a carnot cycle is 1/6.If on reducing the temperature of the sink 75 degrees celcius ,the efficiency becomes 1/3,determine he initial and final temperatures between which the cycle is working.

Answers

Answer:

450°C

Explanation: Given that the efficiency of Carnot engine if T₁ and T₂ temperature are initial and final temperature .

η = 1 - T2 / T1

η = 1/6 initially

when T2 is reduced by 65°C then η becomes 1/3

Solution

η = 1/6

1 - T2 / T1 = 1/6 [ using the Formula ]........................(1)

When η = 1/3 :

η = 1 - ( T2 - 75 ) / T1

1/3 = 1 - (T2 - 75)/T1.........................(2)

T2 - T1 = -75 [ because T2 is reduced by 75°C ]

T2 = T1 - 75...........................(3)

Put this in (2) :

> 1/3 = 1 - ( T1 - 75 - 75 ) / T1

> 1/3 = 1 - (T1 - 150 ) /T1

> (T1 - 150) / T1 = 1 - 1/3

> ( T1 -150 ) / T1 = 2/3

> 3 ( T1 - 150 ) = 2 T1

> 3 T1 - 450 = 2 T1

Collecting the like terms

3 T1- 2 T1 = 450

T1 = 450

The temperature initially was 450°C

Suppose that a 0.275 m radius, 500 turn coil produces an average emf of 11800 V when rotated one-fourth of a revolution in 4.42 ms, starting from its plane being perpendicular to the magnetic field.

Required:
Find the magnetic field strength needed to induce an average emf of 10,000 V.

Answers

Answer:

The magnetic field strength : 0.372 T

Explanation:

The equation of the induced emf is given by the following equation,

( Equation 1 ) emf = - N ( ΔФ / Δt ) - where N = number of turns of the coil, ΔФ = change in the magnetic flux, and Δt = change in time

The equation for the magnetic flux is given by,

( Equation 2 ) Ф = BA( cos( θ ) ) - where B = magnetic field, A = area, and θ = the angle between the normal and the magnetic field

The area of the circular coil is a constant, as well as the magnetic field. Therefore the change in the magnetic flux is due to the angle between the normal and the magnetic field. Therefore you can expect the equation for the change in magnetic flux to be the same as the magnetic flux, but only that there must be a change in θ.

( Equation 3 ) ΔФ = BA( Δcos( θ ) )

Now as the coil rotates one-fourth of a revolution, θ changes from 0 degrees to 90 degrees. The " change in cos θ " should thus be the following,

Δcos( θ ) = cos( 90 ) - cos( 0 )

= 0 - 1 = - 1

Let's substitute that value in the third equation,

( Substitution of Δcos( θ ) previously, into Equation 3 )

ΔФ = BA( - 1 ) = - BA

Remember the first equation? Well if the change in the magnetic flux = - BA, then through further substitution, the emf should = - N( - BA ) / Δt. In other words,

emf =  - N( - BA ) / Δt,

emf = NBA / Δt,

B = ( emf )Δt / NA

Now that we have B, the magnetic field strength, isolated, let's solve for the area of the circular coil and substitute all known values into this equation.

Area ( A ) = πr²,

= π( 0.275 )² = 0.2376 m²,

B = ( 10,000 V )( 4.42 [tex]*[/tex] 10⁻³ s ) / ( 500 )( 0.2376 m² ) = ( About ) 0.372 T

The magnetic field strength : 0.372 T

Two small plastic spheres are given positive electrical charges. When they are 20.0 cm apart, the repulsive force between them has magnitude 0.200 N.


1. What is the charge on each sphere if the two charges are equal? (C)


2. What is the charge on each sphere if one sphere has four times the charge of the other? (C)

Answers

Answer:

A. 2.97x 10^-6C

B. 1.48x10^ -6 C

Explanation:

Pls see attached file

Answer:

1) +9.4 x 10^-7 C

2) +4.72 x 10^-7 C  and  +1.9 x 10^-6 C

Explanation:

The two positive charges will repel each other

Repulsive force on charges = 0.200 N

distance apart = 20.0 cm = 0.2 m

charge on each sphere = ?

Electrical force on charged spheres at a distance is given as

F = [tex]\frac{kQq}{r^{2} }[/tex]

where F is the force on the spheres

k is the Coulomb's constant = 8.98 x 10^9 kg⋅m³⋅s⁻²⋅C⁻²

Q is the charge on of the spheres

q is the charge on the other sphere

r is their distance apart

since the charges are equal, i.e Q = q, the equation becomes

F = [tex]\frac{kQ^{2} }{r^{2} }[/tex]

making Q the subject of the formula

==> Q = [tex]\sqrt{\frac{Fr^{2} }{k} }[/tex]

imputing values into the equation, we have

Q = [tex]\sqrt{\frac{0.2*0.2^{2} }{8.98*10^{9} } }[/tex] = +9.4 x 10^-7 C

If one charge has four times the charge on the other, then

charge on one sphere = q

charge on the other sphere = 4q

product of both charges = [tex]4q^{2}[/tex]

we then have

F = [tex]\frac{4kq^{2} }{r^{2} }[/tex]

making q the subject of the formula

==> q =  [tex]\sqrt{\frac{Fr^{2} }{4k} }[/tex]

imputing values into the equation, we have

q = [tex]\sqrt{\frac{0.2*0.2^{2} }{4*8.98*10^{9} } }[/tex] = +4.72 x 10^-7 C

charge on other sphere = 4q = 4 x 4.72 x 10^-7 = +1.9 x 10^-6 C

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