Which of the following is NOT a reason why humans sleep?

Sleep helps to restore and repair brain tissue.

Sleep restores and rebuilds memories.

Sleep provides a psychic safety valve to discharge unacceptable feelings.

During sleep, growth hormone is released, especially in children.

Answer:

False.

Explanation:

The voltage of a disconnected charged capacitor decreases when the plates are brought closer together because the capacitance is inversely proportional to the area. If the area between plates decreases, its capacitance increases and vice versa. There is direct relationship between voltage of a disconnected charged capacitor and plates. If the distance between plates decreases, the voltage of a disconnected charged capacitor is also decreases while on the other hand, if the distance between plates increases, the voltage of a disconnected charged capacitor is also increases.

Answer:

The correct answer is -

B. The velocity would double (v = 2v).

C. The wavelength would be half (λ = λ/2).

Explanation:

A wave has a speed or velocity that is related to the wavelength of the wave and the frequency of the wave and this relationship can be represented by the following equation-

Wave velocity V = Wavelength (λ) * Frequency (f)

Frequency (f) = Velocity (V) / Wavelength(λ).

The frequency and wavelength are inversely proportional and frequency and velocity are directly proportional to each other.

So, if f = 2f then,

putting value in the formula,

2f = 2v/λ, which means, f = 2v and f = λ/2

when the frequency is doubled, the wavelength will be halved and velocity will be doubled.

Answer: A. Ar

Explanation: not anything else besides Ar

Answer: 3.13 m

Explanation:

Given

mas of the ball is m=10 kg

The ball rolls down a vertical distance of 5 m

Spring constant of spring is [tex]k=100\ N/m[/tex]

Here, the potential energy of the ball converted into kinetic energy which in turn converts into elastic potential energy

[tex]\Rightarrow mgh=\frac{1}{2}kx^2\quad [\text{x=compression in the spring}]\\\\\Rightarrow 10\times 9.8\times 5=\frac{1}{2}\cdot 100\cdot x^2\\\Rightarrow x=\sqrt{9.8}\\\Rightarrow x=3.13\ m[/tex]

Thus, the spring compresses by 3.13 m.

Answer:

Explanation:

The law is about how object will be deformed when certain amount force is  applied. Elastic limit is a point where object will not return its previous shape after being deformed

Answer:

Option A

Explanation:

The graph for this problem must depict the following ""Increased allocation of resources to reproduction relative to growth diminished future fecundity."

Hence, the survivor ship must be on the Y axis and the resources on the X axis.

Here the resources include the number of seeds produced.

hence, the higher is the number of seeds (resource), the lower is the survivorship (future fecundity)

Hence, option A is correct

Answer:

i have no idea i came here to find out too :(

Explanation:

Answer:

F = 51.3°

Explanation:

The component of weight parallel to the inclined plane must be responsible for the rolling back motion of the car. Hence, the force required to be applied by the child must also be equal to that component of weight:

[tex]F = Parallel\ Component\ of\ Weight\ of\ Wagon= WSin\theta\\[/tex]

where,

W = Weight of Wagon = 150 N

θ = Angle of Inclinition = 20°

Therefore,

[tex]F = (150\ N)Sin\ 20^o[/tex]

F = 51.3°

Answer:

Explanation:

Density = Mass / Volume = 850 / 40*10*5 = 0.425 g /cm^3

Answer:

f = 4.67 cm

Explanation:

Here, we can use the thin lens formula, as follows:

[tex]\frac{1}{f}= \frac{1}{p}+ \frac{1}{q}\\\\[/tex]

where,

f = focal length of lens = ?

p = distance of object from lens = 12.4 cm

q = distance of image from lens = 7.5 cm

Therefore,

[tex]\frac{1}{f} =\frac{1}{12.4\ cm} +\frac{1}{7.5\ cm}\\\\\frac{1}{f} = \frac{1}{4.67\ cm}[/tex]

f = 4.67 cm

Answer:

 y_lower = 0.915 m,   y_superior = 1,905 m

Explanation:

In this exercise we use the law of reflection for a flat mirror.

         θ’= θ

To see the feet of the person a ray of light that part of them must reach the bottom of the mirror and its reflection has to reach the eyes.

As the law of reflection the incident and reflected angles are equal, the distance from the floor to the point where the two rays (incident and reflected) touch the mirror must be symmetrical, oses from the floor

           y = 1.83 / 2

           y = 0.915 m

To see the head, a ray of light that comes from the tip of the head and is reflected in the mirror must reach the eyes. As the head is 0.15 m above the eyes and the incident and reflected rays have the same angle, the mirror must be at half the height, that is, the mirror is 0.075 m below the tip of the head.

In summary

* the bottom of the mirror is 0.915 m from the ground

* the top of the mirror is at 1.83 + 0.075

                 y_superior = 1,905 m

ground

Answer:

gravity

Explanation:

I don't know what the explanations would be

Answer:

convex       f = 33 cm

concave     f = -33 cm

Explanation:

In geometric optics the focal length of a lens is given by

         [tex]\frac{1}{f} = ( n-1) \ (\frac{1}{R_2} - \frac{1}{R_1} )[/tex]

where n is the refractive index of the medium, R₁ and R₂   are the focal lengths on each side of the lens.

In this case one of the sides is flat so its focal length is infinite, if the lens is convex the focal length is positive, convergent lens and if it is concave the focal length is negative, divergent lens.

         [tex]\frac{1}{f} = (n-1) \ \frac{1}{R}[/tex]

the refractive index of the glass is n = 1.5

let's calculate

         1 / f = (1.5 -1) 1 / 16.5

         1 / f = 0.03030

          f = 33 cm

convex       f = 33 cm

concave     f = -33 cm

Answer:

5.0-5.5 is the answer to your question

Answer:

Gy = 3.14x10⁻⁴ Gy

Explanation:

To get the dose in Gy we need to use the following expression:

Gy = E / m  (1)

Where:

Gy: dose

E: energy absorbed per atom

m: mass of the human body.

We don't have the energy per atom, but we can calculate that by following the next procedure.

First, let's determine the number of atoms of potassium in our body. For that we need to determine the moles in the 140 g of potassium, with the molecular mass and then, use the avogadro's number:

moles = m/MM

moles = 140 / 39.1 = 3.58 moles

N° atoms = 3.58 * 6.02x10²³ atoms = 2.16x10²⁴ atoms of K.

The abundance of the ⁴⁰K is 0.012% so the atoms of this isotope would be:

N = 2.16x10²⁴ * (0.012/100) = 2.59x10²⁰ atoms of ⁴⁰K.

With this number, and the half life rate, we can determine the number of decay atoms in a year (λ) using the following expression:

λ = ln2 / t(1/2)

λ = ln2 / 1.3x10⁹ = 5.33x10⁻¹⁰ year⁻¹

This number, multiplied by the number of atoms:

R = 5.33x10⁻¹⁰ * 2.59x10²⁰ = 1.38x10¹¹ atoms/year

Now, each atom of K gives an average energy of 1 MeV, so with the atoms we have:

E = 1.38x10¹¹ * 1x10⁶ eV = 1.38x10¹⁷ eV

This value can be expressed in Joules so:

E = 1.38x10¹⁷ eV * (1 J / 6.24x10¹⁸ eV) = 0.022 J

Finally, we can use (1) to get the dose in Gy:

Gy = 0.022 / 70

Hope this helps

Answer:

Solution given:

Radius of small sphere[r]=5cm=0.05m

Radius of large sphere[R]=10cm=0.1m

capacitance of small sphere[c]=4πε0r

=[tex]4π*8.85×10^{-12}×0.05=5.56*10^{-12}F[/tex]

Charge for small sphere[Q1]=100C

Charge for small sphere[Q2]=50C

Potential difference [V1]=[tex] \frac{charge}{capacitance}=\frac{100}{5.56*10^{-12}}=1.8×10^{13}[/tex]V

.

again

capacitance of small sphere[C]=4πε0R

=[tex]4π*8.85×10^{-12}×0.1=1.11*10^{-11}F[/tex]

Potential difference [V2]=[tex] \frac{charge}{capacitance}=\frac{50}{1.11*10^{-11}}=4.5×10^{12}[/tex]V

Now

Loss of energy:

[tex] \frac{cC(V1-V2)^{2}}{2(c+C)}[/tex]

=[tex] \frac{5.56*10^{-12}*1.11*10^{-11}(1.8*10^{13}-4.5*10^{12})^{2}}{2(5.56*10^{-12}+1.11*10^{-11})}[/tex]

=25Joule

Answer:

The total resistance is 106 Ω and the current in the circuit is 0.11 A.

Explanation:

Given that,

Voltage of the battery, V = 12 V

Resistors 34 Ω, 42Ω, and 30Ω are connected in series.

The total resistance is given by :}

R = 34 + 42 +30

= 106Ω

Let I is the total current in the circuit. Using ohm's law to find it such that,

[tex]I=\dfrac{V}{R}\\\\I=\dfrac{12}{106}\\\\I=0.11\ A[/tex]

Hence, the total resistance is 106 Ω and the current in the circuit is 0.11 A.

Answer:

2 m/s²

Explanation:

From the question given above, the following data were obtained:

Initial velocity (u) = 0 m/s

Final velocity (v) = 12 m/s

Time (t) = 6 s

Acceleration (a) =?

The acceleration of the player can be obtained as follow:

v = u + at

12 = 0 + (a × 6)

12 = 6a

Divide both side by 6

a = 12 / 6

a = 2 m/s²

Thus, the acceleration of the player is 2 m/s²

Answer:

E = 1.711 MeV

Explanation:

From the law of the conservation of energy:

[tex]K.E_{e}+K.E_p + E_{e}+E_{p} = 2 E[/tex]

where,

[tex]K.E_e=K.Ep=[/tex] the kinetic energy of positron and electron = 1.2 MeV

[tex]E_e=E_p =[/tex] Rest energy of the electron and the positron = 0.511 MeV

E = Energy of Photon = ?

Therefore,

[tex]1.2\ MeV + 1.2\ MeV + 0.511\ MeV + 0.511\ MeV = 2E\\\\E = \frac{3.422\ MeV}{2}\\\\[/tex]

E = 1.711 MeV

Answer:

D

Explanation:

Answer:

a = 0.1962 m/s^2

Explanation:

The magnitude of kinetic friction exerted is given by

[tex]F_k=\mu_kN[/tex]

Where, μ_k= coefficient of kinetic friction= 0.02 and N = reaction force = mg

Where m= mass = 30 Kg and, g is acceleration due to gravity =9.81 m/s^2

F_k=0.02×30×9.81 =5.886 N

Now, since, there is no applied force this kinetic friction force will cause acceleration of the child

⇒ ma = F_k

here, a is the acceleration

⇒30a = 5.886

⇒ a = 0.1962 m/s^2

Answer:

A)    q₂ = 75.98 cm, B)     q₂' = 115.38 cm, C)

Explanation:

A) This is an exercise in geometric optics, as the two lenses are separated by a greater distance than their focal lengths from each lens, they must be worked as independent lenses.

Lens 1. More to the left

let's use the constructor equation

         [tex]\frac{1}{f} = \frac{1}{p} + \frac{1}{q}[/tex]

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

We must assume a distance to the object to perform the calculation, suppose that the object is 50 cm from lens 1 that is further to the left of the system.

          [tex]\frac{1}{q_1} = \frac{1}{f} - \frac{1}{p}[/tex]

         [tex]\frac{1}{q_1} = \frac{1}{14.8} - \frac{1}{50}[/tex]  

          1 / q₁ = 0.04756

           q₁ = 21.0227 cm

this image is the object for the second lens that has f₂ = 14.8 cm

the distance must be measured from the second lens

          p₂ = 39.4 -q₁

          p₂ = 39.4 -21.0227

          p₂ = 18.38 cm

let's use the constructor equation

            1 / q₂ = 1 / f - 1 / p2

             [tex]\frac{1}{q_2} = \frac{1}{14.8} - \frac{1}{18.38}[/tex]

            [tex]\frac{1}{q_2}[/tex] = 0.01316

            q₂ = 75.98 cm

measured from the second lens

B) the position of the final image with respect to the first lens is

            q₂’= q₂ + 39.4

             q₂'= 75.98 +39.4

              q₂' = 115.38 cm

C) the magnification of a lens is

              m = - q / p

in this case the image measured from lens 2 is q2 = 75.98 cm

the distance to the object from the first lens is p1 = 50cm

          m = - 75.98 / 50

          m = -1.5 X

the negative sign indicates that the image is inverted

Answer:

C

Explanation:

edge 2020... Using elimination it's the only one that makes sense.

The statement third "an increase in the distance between the objects causes a greater change in the gravitational force than the same increase in mass" is correct.

The gravitational force is a force that attracts all mass-bearing objects. The gravitational force is referred to as attractive because it always strives to pull masses together rather than pushing them apart.

As we know, the gravitational force is given by:

[tex]\rm F = \dfrac{Gm_1m_2}{r^2}[/tex]

Where, G is the gravitational constant.

m1 and m2 are masses.

r is the distance between the masses.

From the data given in the table, shows that:

The gravitational force is indirectly proportional to the square of the distance.

Thus, the statement third "an increase in the distance between the objects causes a greater change in the gravitational force than the same increase in mass" is correct.

Learn more about the gravitational force here:

https://brainly.com/question/12528243

#SPJ2

Answer:

M = 1.90 Kg

Explanation:

Given data: mass = 2.5 Kg

radius R = 0.8 m

angular velocity ω = 1.5 rad/s

Angular momentum L =0.5×Iω^2

Where, I  is the moment of inertia of the spinning disc.

I = 0.5MR^2

I = 0.5×2.5×0.8^2

I = 0.8 Kg/m^2

Then L = 0.5×0.8×1.5^2 = 0.8×2.25 = 0.9 Kg-m^2/sec

Let unknown mass be M

New mass of disc = (2.5+M) Kg, R = 0.8 m

New I = 0.5(2.5+M)(0.8)^2

Since, angular momentum is conserved

Angular momentum before = angular momentum after

0.5×0.5(2.5+M)(0.8)^2×(1.13)^2 = 0.9

Solving for M we get

0.204304(2.5+M)=0.9

M = 1.90 Kg

Answer:

P = 756.84 Watts

Explanation:

As the tension is stationary or innitial, T₀ = 31 N, the mean would be:

T₁ + T₂ / 2 = T₀    (1)

T₁ + T₂ = 2 * 31 = 62 N

Now, with the following expression we can determine the linear speed:

V = πWD  (2)

W: angular speed of the wheel  (rev/s)

D: diameter of the wheel (in meters)

W = 1547 rev/min * (1 min/60 s) = 25.78 rev/s

V = π * 25.78 * 0.379 = 30.695 m/s

We also know that:

T₁ / T₂ = exp (μθ)

T₁ = T₂ exp(μθ)   (3)

We already have those values so replacing:

T₁ = T₂ exp(0.3 * 161 * π/180)

T₁ = 2.32T₂   (4)

We can now replace (4) in (1) like this:

T₁ + T₂ = 62 N

2.32T₂ + T₂ = 62

3.32T₂ = 62

T₂ = 18.67 N

Which means that T₁:

T₁ = 2.32(18.67)

T₁ = 43.33 N

Finally, the power can be determined using the following expression:

P = (T₁ - T₂)V  (5)       Replacing we have:

P = (43.33 - 18.67)*30.695

Hope this helps