Question

A sled and rider with a combined weight of 70.0 kg are at rest on the top of a hill 11.0 m high. (Enter your answers in J.) Assuming there is no friction, what would the total energy be on sliding halfway down the hill?answer with:___ J

Answer 1

We know that at the top of the 11 m hill the sled and rider are at rest, which means that all the energy at this point is potential energy; the potential energy is given by:

`U=mgh`

Plugging the values given we have:

`\begin{gathered} U=(70)(9.8)(11) \\ U=7546 \end{gathered}`

Hence at the top of the hill the total energy is 7546 J.

Now, from conservation of energy and since there is no friction, we know that at any point of the motion the total energy is the same as the starting energy.

Therefore, the total energy halfway the hill is 7546 J.

Note: At this point we would expect the potential energy to be half of what it was at the top of the hill and the other half will be kinetic energy; nonetheless the total energy, which is the sum of the kinetic and potential energy, has to remain the same as the initial energy.