Question

Alana explains when a ball sitting on top of a grassy hill rolls down the hill.

The motionless ball has potential energy. Once the ball starts to roll down the hill, new kinetic energy is made. As the ball rolls across the grass, it slows down. The kinetic energy of the ball is converted to other forms of energy.

Which best describes Alana’s error?

A. The motionless ball does not have energy because it is still.
B. Kinetic energy is not made; it is a result of energy transformation.
C. The ball cannot slow down unless someone touches it.
D. The energy is not converted; it disappears.

Answer 1

Before I try to really help you with this question. Try read the explanation really closely, and give me a qualified guess.

Answer 2

Well i know it's not A because if someone kicks a ball and it's stops rolling it still has energy, so i would have to think it is B

Answer 3

That is very true. Can you try explain why it is B? :)

Answer 4

Well say someone kick a soccer ball then there is energy in the ball and the object that was used to hit or kick the ball, so i would think there is energy transformation of potential energy

Answer 5

Exactly. You answered your own question. :)

In basic energy can't be created nor destroyed. So again lets assume we got a ball with a specific potential energy in the height \(h\) you let the ball start rolling down this hill as the velocity increases so does the kinetic energy. It should the be evident that just before grass begins to flatten out the velocity is the highest and so is the kinetic energy.
But it leaves one question, why does the ball then stop after a little when it has lost some of it's potential energy? The answer to that lies in the fact you transfer some of the energy to the surroundings due to the air resistance, the thermal energy in the grass and so on.