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Snezhnost [94]
3 years ago
9

A book is falling from the top shelf of a bookcase. Which statement correctly describes the change in the energy of the book? a.

The potential energy and kinetic energy remain the same. b. The potential energy decreases as kinetic energy increases. c. The kinetic energy decreases as potential energy increases. d. The kinetic energy remains at zero, but potential energy increases.
Physics
2 answers:
valentina_108 [34]3 years ago
6 0

Answer:

Correct answer letter b.

Explanation:

When the book is on the top shelf of the bookcase, it just only gravitational potential energy, due to the gravitational field and the kinetic energy at this point is zero because the book is at rest.

Now, when the book starts falling, all the potential energy will transform into the kinetic energy. It happens, thanks to the conservation of the energy,that says energy can neither be created nor destroyed, energy can only be transferred or changed from one form to another.

Let's recall that the gravitational potential energy depends on the object's position, so when the book falls, the magnitude of the position decreases and the speed of this object increases.

Therefore, the potential energy of the book decreases as kinetic energy increases.

Correct answer letter b.

I hope it helps you!  

Evgesh-ka [11]3 years ago
6 0

Answer:

B

Explanation:

Just took the quiz on edge! hope this helps

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1)the car's engine power is 44000W. Explain this number in a physical sense
Ratling [72]

Answer:

1) It expresses the rate (top speed) at which it can move with time.

2) P = 20 W

3) h = 18 km

Explanation:

1) Power is the rate of transfer of energy.

⇒ Power = \frac{Energy(or workdone)}{Time}

i.e P = \frac{E}{t}

Thus a car's engine power is 44000W implies that the engine of the car can propel the car at this rate. This expresses the rate (top speed) at which it can move with time.

2) m = 400g = 0.4 kg

    t = 20 s

h = 100m

g = 10 m/s^{2}

P = \frac{mgh}{t}

  = \frac{0.4*10*100}{20}

  = \frac{400}{20}

P = 20 W

3) u = 600 m/s

   g = 10 m/s^{2}

From the third equation of free fall,

V^{2} = U^{2} - 2gh

V is the final velocity, U is the initial velocity, h is the height.

0 = (600)^{2} - 2 x 10 x h

0 = 360000 - 20h

20h = 360000

h = \frac{360000}{20}

  = 18000

h = 18 km

The maximum height of the bullet would be 18 km.

3 0
3 years ago
The age and crisis of the stage trust vs. mistrust
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Hope it is helpful
6 0
3 years ago
A child is riding a merry-go-round that has an instantaneous angular speed of 12 rpm. If a constant friction torque of 12.5 Nm i
sammy [17]

Answer:

-0.25 rad/s^2

Explanation:

The equivalent of Newton's second law for rotational motions is:

\tau = I \alpha

where

\tau is the net torque applied to the object

I is the moment of inertia

\alpha is the angular acceleration

In this problem we have:

\tau = -12.5 Nm (net torque, with a negative sign since it is a friction torque, so it acts in the opposite direction as the motion)

I=50.0 kg m^2 is the moment of inertia

Solving for \alpha, we find the angular acceleration:

\alpha = \frac{\tau}{I}=\frac{-12.5 Nm}{50.0 kg m^2}=-0.25 rad/s^2

3 0
3 years ago
When a car of mass 1167 kg accelerates from 10.0 m/s to some final speed, 4.00  10 5J of work are done. Find this final speed.
Akimi4 [234]
  • Mass=1167kg
  • Initial velocity=u=10m/s
  • Acceleration=a=4m/s^2
  • Work done=105J=W
  • Final velocity=v=?
  • Force=F
  • Distance=d

Apply Newton's second law

\\ \tt\hookrightarrow F=ma

\\ \tt\hookrightarrow F=1167(4)=4668N

Now

\\ \tt\hookrightarrow W=Fd

\\ \tt\hookrightarrow d=\dfrac{W}{F}

\\ \tt\hookrightarrow d=\dfrac{105}{4668}

\\ \tt\hookrightarrow d=0.022m

Now

  • d be s

According to third equation of kinematics

\\ \tt\hookrightarrow v^2=u^2+2as

\\ \tt\hookrightarrow v^2=10^2+2(4)(0.022)

\\ \tt\hookrightarrow v^2=100+8(0.022)

\\ \tt\hookrightarrow v^2=100+0.176

\\ \tt\hookrightarrow v^2=100.176

\\ \tt\hookrightarrow v=10.001m/s

8 0
2 years ago
What is the wavelength of a photon whose energy is twice that of a photon with a 600 nm wavelength?
bearhunter [10]
Planck's equation states that
E = hf
where
E =  the energy,
h = Planck's constant
f =  the frequency

Because
c = fλ
where
c =  velocity of light,
λ = wavelength
therefore
E = h(c/λ)

Photon #1:
The wavelength is λ₁ = 60 nm.
The energy is
E₁ = (hc)/λ₁

Photon #2:
The energy is twice that of photon #1, therefore its energy is
E₂ = 2E₁ = (hc)/λ₂.

Therefore
\frac{E_{2}}{E_{1}}= \frac{(hc)/\lambda_{2}}{(hc)/60 \, nm} =2\\ \frac{60}{\lambda_{2}} =2 \\ \lambda_{2} =  \frac{60}{2} =30 \, nm

Answer:  30 nm

8 0
2 years ago
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