The driver of a stationary car hears a siren of an approaching police car at a frequency of 280Hz. If the actual frequency of the siren is 240Hz, find the speed of the police car (speed of sound is 343m/s).

Answer:

(a) The current needed is 56.92 A

(b) The magnitude of the magnetic field inside the solenoid is 0.134 T

(c) The energy density inside the solenoid is 7.144 kJ/m³

Explanation:

Given;

energy stored in the magnetic field of solenoid, E = 8.1 J

number of turns of the solenoid, N = 620 turns

diameter of the solenoid, D = 6.6 cm = 0.066 m

radius of the solenoid, r = D/2 = 0.033 m

length of the solenoid, L = 33 cm = 0.33 m

Inductance of the solenoid is given as;

[tex]L= \frac{\mu_o N^2 A}{l}[/tex]

where;

A is the area of the solenoid = πr² = π (0.033)² = 0.00342 m²

μ₀ is permeability of free space = 4π x 10⁻⁷ H/m

[tex]L= \frac{4\pi*10^{-7} *620^2 *0.00342}{0.33} \\\\L = 0.005 \ H[/tex]

(A). How much current needed

Energy stored in magnetic field of solenoid is given as;

[tex]E = \frac{1}{2} LI^2\\\\[/tex]

Where;

I is the current in the solenoid

[tex]E = \frac{1}{2} LI^2\\\\I^2 = \frac{2E}{L}\\\\I = \sqrt{\frac{2*8.1}{0.005}}\\\\ I = 56.92 \ A[/tex]

(B) The magnitude of the magnetic field inside the solenoid

B = μ₀nI

where;

n is number of turns per unit length

B = μ₀(N/L)I

B = (4π x 10⁻⁷)(620/0.33)(56.92)

B = 0.134 T

(C) The energy density (energy/volume) inside the solenoid

[tex]U_B = \frac{B^2}{2\mu_0} \\\\U_B = \frac{(0.134)^2}{2*4\pi*10^{-7}} \\\\U_B = 7143.54 \ J/m^3\\\\U_B = 7.144 \ kJ/m^3[/tex]

Answer:

C) experience a small induced magnetic moment when placed in an external magnetic field.

Explanation:

Diamagnetics materials are those that experience a small induced magnetic moment when placed in an external magnetic field. These materials, such as bismuth, copper, silver and lead, have elementary magnets in their compositions. When they are exposed to an external magnetic cap, these elemental magnets tend to follow an orientation contrary to the external magnetic field. As a result, a magnetic field is created in the opposite direction to the external magnetic field.

Explanation:

It is given that, in the first trial, the initial velocity is [tex]v_o[/tex] and in the second it is [tex]4v_o[/tex].

The total energy of the system remains constant. So,

[tex]\dfrac{1}{2}mv^2+\dfrac{1}{2}kx^2=\text{constant}[/tex] ....(1)

x is amplitude

It means that the amplitude is directly proportional to velocity. If velcoity increases to four times, then the amplitude also becomes 4 times.

Differentiating equation (1) we get :

[tex]mv\dfrac{dv}{dt}+kx\dfrac{dx}{dt}=0[/tex]

Since,

[tex]\dfrac{dv}{dt}=a,\ \text{acceleration}[/tex] and [tex]\dfrac{dx}{dt}=v,\ \text{velocity}[/tex]

So,

[tex]mva+kxv=0[/tex]

It means that the acceleration is also proportional to the amplitude. So, acceleration also becomes 4 times.

Hence, the correct option is (B) "both the amplitude and the maximum acceleration are four times as great"

Answer:

The acceleration of the box is 3 m/s²

Explanation:

Given;

mass of the box, m = 12 kg

horizontal force pulling the box forward, Fx = 48 N

frictional force acting against the box in opposite direction, Fk = 12 N

The net horizontal force on the box, F = 48 N - 12 N

The net horizontal force on the box, F = 36 N

Apply Newton's second law of motion to determine the acceleration of the box;

F = ma

where;

F is the net horizontal force on the box

a is the acceleration of the box

a = F / m

a = 36 / 12

a = 3 m/s²

Therefore, the acceleration of the box is 3 m/s²

Answer:

μ = 0.03

Explanation:

In order for the trunk not to slide the frictional force between the turntable and the trunk must be equal to the unbalanced force applied on the trunk by the motion of the turntable. Therefore,

Unbalanced Force = Frictional Force

but,

Unbalanced Force = ma (Newton's second law of motion)

Frictional Force = μN = μW = μmg

Therefore,

ma = μmg

a = μg

μ = a/g

where,

μ = coefficient of static friction between the trunk and the turntable = ?

a = tangential acceleration of trunk = 0.3 m/s²

g = 9.8 m/s²

Therefore,

μ = (0.3 m/s²)/(9.8 m/s²)

μ = 0.03

Answer:

Explanation:

Using the law of gravitation of force to solve this question. The law states that the Force of attraction between two masses is directly proportional to the product of their masses and inversely proportional to the square of the distances between them.

Mathematically, F = GMaMb/R² ... 1

G is the gravitational constant

Ma and Mb are the masses of the balls

R is the distance between the balls

If the mass of ball B is tripled and the magnitude of the separation of the balls is increased to 3R, the force between them will be;

F₂ = GMa(3Mb)/(3R)²

F₂ = 3GMaMb/9R² ... 2

Dividing equation 1 by 2 we will have;

F₂/F = (3GMaMb/9R²)/GMaMb/R²

F₂/F =  3GMaMb/9R² * GMaMb/R²

F₂/F = 3/9

F₂/F = 1/3

F₂ = 1/3 F

This shows that the magnitude of the new attractive force is one-third that of the initial attractive force

Answer:

a) 1764.71 ohms

b) 1.73 H

Explanation:

From the question, we can identify the following parameters;

Vo =12 V , i = 4.86 mA, t =0.700 ms, io =6.80 mA

(a) Indcued emf V = L di/dt =0

From ohms law Vo = ioR

R = 12/6.80*0.001

R=1764.71 ohms

(b) For LR circuit

i =io (1-e^-t/T)

Time constant T = L/R

4.86 = 6.80 (1-e^-0.7*10^-3/T)

divide both side by 6.8

0.715 = 0.0007/T

L/R = 0.0007/0.715

L/R = 0.000979020979

Substitute R from above

L = 0.000979020979 * 1764.71

L =1.73 H

Answer:

Acceleration(a) = 2.588 m/s²

TL = 230.784 N

TR = 220.5 N

Explanation:

Given:

M = 7.95 kg

mL = 32 kg

mR = 17.8 kg

g = 9.8 m/s²

Find:

Acceleration(a)

TL

TR

Computation:

Acceleration(a) = [(mL - mR)g] / [mL + mR + M/2]

Acceleration(a) = [(32 - 17.8)9.8] / [32 + 17.8 + 7.95/2]

Acceleration(a) = [139.16] / [53.775]

Acceleration(a) = 2.588 m/s²

TL = mL(g-a)

TL = 32(9.8-2.588)

TL = 230.784 N

TR = mR(g+a)

TR = 17.8(9.8+2.588)

TR = 220.5 N

Answer:

Magnitude of the magnetic field inside the solenoid near its centre is 1.293 x 10⁻³ T

Explanation:

Given;

number of turns of solenoid, N = 269 turn

length of the solenoid, L = 102 cm = 1.02 m

radius of the solenoid, r = 2.3 cm = 0.023 m

current in the solenoid, I = 3.9 A

Magnitude of the magnetic field inside the solenoid near its centre is calculated as;

[tex]B = \frac{\mu_o NI}{l} \\\\[/tex]

Where;

μ₀ is permeability of free space = 4π x 10⁻⁷ m/A

[tex]B = \frac{4\pi*10^{-7} *269*3.9}{1.02} \\\\B = 1.293 *10^{-3} \ T[/tex]

Therefore, magnitude of the magnetic field inside the solenoid near its centre is 1.293 x 10⁻³ T

Answer:

4.41 m/s^2

Explanation:

(v_f)^2 - (v_i)^2 = 2a * change in distance

(21)^2 - (0)^2 = 2a * 50

a = (21^2)/(2*50)

a = 4.41 m/s^2

Answer:

  x_total = 0.17m

Explanation:

We can treat this exercise with the kinematics equations, where in the first part it is accelerated and in the second it is a uniform movement.

Let's analyze accelerated motion

The time that lasts is t = 20 10⁻³ s, the initial speed is zero (v₀ = 0), let's find the length that advances

            x₁ = v₀ t + ½ a t²

            x₁ = ½ a t²

            x₁ = ½ 210 (20 10⁻³)²

            x₁ = 4.2 10⁻² m

let's find the speed for the end of this movement

            v = v₀ + a t

            v = 0 + 210   20 10⁻³

            v = 4.2 m / s

with this speed we can find the distance that the uniform movement

           x₂ = v t2

           x₂ = 4.2   30 10⁻³

           x₂ = 1.26 10⁻¹ m

           x₂ = 0.126m

the total distance traveled is

          x_total = x₁ + x₂

          x_total = 0.0420 +0.126

          x_total = 0.168m

     Let's reduce the significant figures to two

          x_total = 0.17m

Answer:

A.ENERGY: Radio<microwaves<infrared<visible light<ultraviolet<xrays<gammarays

B. WAVELENGTH: Radio>microwaves> infrared>visible light>ultraviolet>xray> gammarays

C. FREQUENCY: Radio<microwaves<infrared<visible light<ultraviolet<xray< gammarays

Explanation:

THIS IS BECAUSE OF THE FOLLOWING EQUATIONS

1.ENERGY (E)= hX freqency

So as energy of radiation increases frequency also increases

2. Velocity (v) = wavelength x frequency

So as wavelength increases frequency decreases and vice versa

Answer:

12.6 m/s²

Explanation:

First, convert to m/s.

100 km/h × (1000 m/km) × (1 hr / 3600 s) = 27.8 m/s

a = Δv / Δt

a = (0 m/s − 27.8 m/s) / 2.2 s

a = -12.6 m/s²

Answer:

a

The  speed of  wave is   [tex]v_1 = 129.1 \ m/s[/tex]

b

The new speed of the two waves is [tex]v = 129.1 \ m/s[/tex]

Explanation:

From the question we are told that

    The mass of the string is  [tex]m = 60 \ g = 60 *10^{-3} \ kg[/tex]

    The length is  [tex]l = 2.0 \ m[/tex]

    The tension is  [tex]T = 500 \ N[/tex]

Now the velocity of the first wave is mathematically represented as

     [tex]v_1 = \sqrt{ \frac{T}{\mu} }[/tex]

Where  [tex]\mu[/tex] is the linear density which is mathematically represented as

      [tex]\mu = \frac{m}{l}[/tex]

substituting values    

     [tex]\mu = \frac{ 60 *10^{-3}}{2.0 }[/tex]

     [tex]\mu = 0.03\ kg/m[/tex]

So

   [tex]v_1 = \sqrt{ \frac{500}{0.03} }[/tex]

   [tex]v_1 = 129.1 \ m/s[/tex]

Now given that the Tension, mass and length are constant the velocity of the second wave will same as that of first wave (reference PHYS 1100 )

Answer:

processes are competitive and reach a thermal equilibrium where the absorbed energy is equal to the energy emitted, this is the equilibrium temperature of the planet.

Explanation:

The temperature of planet Earth is due to two main types of process, internal and external.

Internal processes are all chemical processes that occur that release heat into the environment or due to gases that trap heat on the planet, greenhouse effect

External processes is heating due to energy coming from the Sun. This includes direct heating of the surface by the absorption of energy and reflects of energy in different atmospheric layers.

These are the two terms that heat the Earth

In addition there are several processes so the planet loses energy,

* energy radiation to outer space that is a few degrees kelvin, for which there is a permanent emission

* endothermic processes that need to absorb heat to perform, this lowers the temperature of the system

* liquid (water) system that absorbs large amounts of heat to change state and temperature.

These processes are competitive and reach a thermal equilibrium where the absorbed energy is equal to the energy emitted, this is the equilibrium temperature of the planet.

Therefore it is impossible for the temperature to increase indefinitely since the emission would increase by decreasing the value

Answer:

They are cooler and wetter

Explanation:

Highland areas have lower temperatures compared to low lying areas. The climate is more wetter because of more rainfalls compared to low lying areas and the wind carries moist air over the highlands.

Answer:

C) 8 m/s²

Explanation:

Given:

v₀ = 40 m/s

v = 0 m/s

Δy = 100 m

Find: a

v² = v₀² + 2aΔy

(0 m/s)² = (40 m/s)² + 2a (100 m)

a = -8 m/s²

Answer:

When we have completely polarized light with intensity I0, and it passes through a polarizing filter with its axis at an angle θ with respect to the light's polarization direction, the new intensity of the light will be:

I = I0*cos^2(θ)

This is called the "Malus' law".

in this case, we have:

I0 =  125 W/m^2

θ = 89.5°

then:

I = (125 W/m^2)*cos^2(89.9°) = 0.00038 W/m^2

Answer:

Explanation:

d

Answer:

Explanation:

a )

Moment of inertial of four masses about axis that coincides with one side :

Out of four masses . location of two masses will lie on the axis so their moment of inertia will be zero .

Moment of inertia of the two remaining masses

= m L² + m L²

= 2 mL²

b )

Axis that bisects two opposite sides

Each of the four masses will lie at a distance of L / 2 from this axis so moment of inertia of the four masses

= 4 x m x ( L/2 )²

= 4 x  mL² / 4

= m L² .

Answer:

The  current in the tube is 0.601 A

Explanation:

Given;

diameter of the fluorescent, d = 3 cm

negative charge flowing in the fluorescent tube, -e = 3 x 10¹⁸ electrons/second

positive charge flowing in the fluorescent tube, +e = 0.75 x 10¹⁸ electrons/ second

The current in the fluorescent tube is due to presence of positive and negative charges to create neutrality in the conductor (fluorescent tube).

Q = It

I = Q/t

where;

I is current in Ampere (A)

Q is charge in Coulombs (C)

t is time is seconds (s)

1 e = 1.602 x 10⁻¹⁹ C

3 x 10¹⁸ e/ s = ?

= (3 x 10¹⁸ e/s  x 1.602 x 10⁻¹⁹ C) / 1e

= 0.4806 C/s

negative charge per second (Q/t) = 0.4806 C/s

positive charge per second (Q/t) =  (0.75 x 10¹⁸ e/s  x 1.602 x 10⁻¹⁹ C) / 1e

positive charge per second (Q/t) = 0.12015 C/s

Total charge per second in the tube, Q / t = (0.4806 C/s + 0.12015 C/s)

                                                                I = 0.601 A

Therefore, the  current in the tube is 0.601 A

Answer:

An open parachute increases the cross-sectional area of the falling skydiver and thus increases the amount of air resistance which he encounters. Once the parachute is opened, the air resistance overwhelms the downward force of gravity.

Explanation:

The larger a parachute, the greater the force.

Hope it helps you in a little way.

Correct answer is 2.7 x 10^-3 J/m3

I hope that helps ! <33

The maximum energy density of the capacitor is closest to: 2.7 x 10^-3 J/m3.

Energy density is defined as the total energy per unit volume of the capacitor. Since, Now, for a parallel plate capacitor, A × d = Volume of space between plates to which electric field E = V / d is confined. Therefore, Energy is stored per unit volume.

All Answers (14) Energy density is equal to 1/2*C*V2/weight, where C is the capacitance you computed and V should be your nominal voltage (i.e 2.7 V). Power Density is V2/4/ESR/weight, where ESR is the equivalent series resistance.

Learn more about energy density at

https://brainly.com/question/13035557

#SPJ2

Answer:

The final velocity of the block after the bullet passes through is 0.66 meters per second.

Explanation:

The interaction between the bullet and the block of woods is a clear example of a perfectly inelastic collision, which can be modelled after the Principle of Momentum Conservation. There are no external forces exerted on the bullet-block system. The equation describing the collision is described below:

[tex]m_{B}\cdot v_{B,o} + m_{W}\cdot v_{W,o} = m_{B}\cdot v_{B,f} + m_{W}\cdot v_{W,f}[/tex]

Where:

[tex]m_{B}[/tex], [tex]m_{W}[/tex]- Masses of the bullet and the block of wood, measured in kilograms.

[tex]v_{B,o}[/tex], [tex]v_{W,o}[/tex] - Initial speeds of the bullet and the block of wood, measured in meters per second.

[tex]v_{B,f}[/tex], [tex]v_{W,f}[/tex]- Final speeds of the bullet and the block of wood, measured in meters per second.

The final speed of the block is cleared:

[tex]v_{W,f} = \frac{m_{B}\cdot (v_{B,o}-v_{B,f})+m_{W}\cdot v_{W,o}}{m_{W}}[/tex]

[tex]v_{W,f} = v_{W,o} + \frac{m_{B}}{m_{W}} \cdot (v_{B,o}-v_{B,f})[/tex]

If [tex]v_{W,o} = 0\,\frac{m}{s}[/tex], [tex]m_{B} = 0.022\,kg[/tex], [tex]m_{W} = 2\,kg[/tex], [tex]v_{B,o} = 210\,\frac{m}{s}[/tex] and [tex]v_{B,f} = 150\,\frac{m}{s}[/tex], then the final velocity of the block after the bullet passes through is:

[tex]v_{W,f} = 0\,\frac{m}{s}+\left(\frac{0.022\,kg}{2\,kg}\right)\cdot \left(210\,\frac{m}{s}-150\,\frac{m}{s} \right)[/tex]

[tex]v_{W,f} = 0.66\,\frac{m}{s}[/tex]

The final velocity of the block after the bullet passes through is 0.66 meters per second.

Answer:

God is omnipresent.

Explanation:

This means God is everywhere and He works where ever we are in the world

Answer:

The correct answer is A    

Explanation:

In this exercise we are given a graph of temperature versus time.

In calorimeter processes there are two types

* one that when giving thermal energy to the system its temperature increases, this fundamentally due to the greater kinetic energy of the molecular ones, this process observes in the graphs as a straight line of constant slope

* A process donates all the thermal energy that is introduced is cracked in breaking the molecular bonds, taking matter from one thermodynamic state to another, for example: liquid to gas.

This process in curves as a horizontal line, that is, there is no temperature change,

When analyzing the graph shown, parts C and D are the one that show a change in temperature with thermal energy. The correct answer is A

Answer:

C and D

Explanation:

Just took the quiz

Answer:

Explanation:

Load will be moved by 4L when effort moves by distance L .

4L = 10 m ( given )

L = 2.5 m

work output = work input = 400 x 10 = 4000 J

work by friction = 100 J

net work output = 3900 J .

efficiency = net output of work / work input

= (3900 / 4000) x 100

= 97.5 %

2 )

work input = 4000 J

distance moved by effort = 2.5 m

If effort be F

F X 2.5  = 4000

F = 1600 N .

Answer:

amplitudes

Explanation:

In everyday physics we define the amplitude of a wave as the maximum (this can also be called the highest)displacement or distance moved by a point on a given vibrating body or wave as measured from its equilibrium position. The key idea in defining the amplitude of a wave motion is the idea of a 'maximum displacement from the position of equilibrium'.

Given the equations;

E= EoSin(kx - ωt)y

B= Bosin(kx- ωt)z

Both Eo and Bo refer to the maximum displacement of the electric and magnetic field components of the electromagnetic wave. This maximum displacement is known as the amplitude of the electric and magnetic components of the electromagnetic wave.

Explanation:

F = kx

mg = kx

(20 kg) (10 m/s²) = (1800 N/m) x

x = 0.11 m

Answer:

negatively charged object attract other negatively objects

Explanation:

opposites attract

Answer:

negativelycharged objects attract other negatively charged objects

Explanation:

unlike charges attract like charges repel