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Andrews [41]
3 years ago
5

A rock falls from the top of a hill to the bottom. The total energy of the rock at the top isn’t the same as the sum of its pote

ntial energy and kinetic energy at the bottom which state meant best explains this situation
A) some of the rocks energy is transformed to thermal energy
B) the rolling rock loses some of its energy because of gravity
C) the rolling rock doesn’t follow the law of conservation of energy
D) the rock absorbs some of its own potential energy
Physics
1 answer:
mart [117]3 years ago
3 0

Answer:

A) some of the rocks energy is transformed to thermal energy

Explanation:

If we neglect air resistance during the fall of the rock, than the mechanical energy of the rock (which is sum of its potential energy and its kinetic energy) would be constant during the entire motion, so the total energy of the rock at the top would be the same as the sum of its potential energy and kinetic energy at the bottom.

However, this not occurs, due to the presence of air resistance. In fact, air resistance acts against the fall of the rock, and because of the friction between the molecules of air and the surface of the rock, the rock loses part of its energy. This energy is converted into thermal energy of the molecules of the air.

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Answer:

We kindly invite you to read carefully the explanation and check the image attached below.

Explanation:

According to this problem, the rocket is accelerated uniformly due to thrust during 30 seconds and after that is decelerated due to gravity. The velocity as function of initial velocity, acceleration and time is:

v_{f} = v_{o}+a\cdot (t-t_{o}) (1)

Where:

v_{o} - Initial velocity, measured in meters per second.

v_{f} - Final velocity, measured in meters per second.

a - Acceleration, measured in meters per square second.

t_{o} - Initial time, measured in seconds.

t - Final time, measured in seconds.

Now we obtain the kinematic equations for thrust and free fall stages:

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v = 30\cdot t (2)

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v = 900-9.81\cdot (t-30) (3)

Now we created the graph speed-time, which can be seen below.

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2 years ago
Give an example to explain that motion is relative in nature
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Answer:

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x = 29 sin 75

x = 28.01m

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