Question

If an object has 100 joules of potential energy (PE) at the top of a ramp, how much kinetic energy (KE) will there be at the other two locations indicated, half-way down the ramp and at the bottom the ramp?
Responses
A 0J and 50J0J and 50J
B 50J and 0J50J and 0J
C 50J and 100J50J and 100J
D 100J and 50J100J and 50J
Question 2
In the first question, we described an energy transformation in a situation without friction. In reality, we almost always must contend with friction when analyzing energy transformations. How would the values change and why?
Responses
A The KE value would decrease. Friction causes some of the energy to be lost.The KE value would decrease. Friction causes some of the energy to be lost.
B The PE-KE values would both decrease due to the presence of friction. Friction opposes motion.The PE-KE values would both decrease due to the presence of friction. Friction opposes motion.
C The KE value would decrease. Friction causes some of the energy to be converted to heat energy.The KE value would decrease. Friction causes some of the energy to be converted to heat energy.
D The PE values would increase but the KE values would decrease. Some of the PE would be converted to heat energy.

Answer 1

Q1: C — 50 J at halfway and 100 J at the bottom.
Explanation: With no friction total mechanical energy is conserved (100 J). Halfway down PE = 50 J so KE = 50 J; at the bottom PE = 0 so KE = 100 J.

Q2: C — The KE value would decrease. Friction causes some of the energy to be converted to heat energy.
Explanation: Friction converts part of the mechanical energy into thermal energy, so less energy is available as kinetic energy.