Question

The entire class goes for a hike. We all pick up rocks from the valley and carry them up to Frenchman Mountain, east of Las Vegas,
where we stack them up on the peak. Subsequently, the pile collapses and all the rocks roll back down the mountain to the valley
below where we originally collected them. Answer the following questions:
1. What energy changed by moving the position of the rocks from the valley to the peak. Explain your answer.
2. What type of energy did the work to move the rocks to the peak? Where did that energy originally come from?
3. What type of energy was used as the rocks rolled back down the mountain?
4. If the rocks were moved from point A (the valley) to point B (the peak) and subsequently rolled back down to point A was the
overall energy used zero since they ended up back where they started? Explain why or why not.

Answer 1

1. gravitational potential energy

Yes, motion energy (kinetic energy) is transformed into gravitational potential energy as the rock falls.

2..When we push a huge rock, there is no transfer of muscular energy to the stationary rock. Also, there is no loss of energy because muscular energy is transferred into heat energy, which causes our body to become hot. From the conservation of energy we know that energy can neither be created nor destroyed, it can only be transformed from one form to another.

3 When the rock starts rolling down the hill it has kinetic energy. When the rock gets to the bottom of the hill and stops, it is no longer in motion therefore it no longer has kinetic energy, the energy has been converted back into potential energy.

Potential energy is transformed to kinetic energy.