Answer:
h = 40 m
Step-by-step explanation:
- Assuming no friction present, total mechanical energy must be conserved, so the following expression stands:
- ΔK + ΔU = 0 (1)
- Now, if the car is at rest at the crest of the hill, the change in kinetic energy is just as follows:
(2)
where vb = speed at the bottom = 28 m/s
- If we define the bottom as our zero reference level for the gravitational potential energy, we can write the following equation:
(3)
- From (1) we get:
- ΔK = -ΔU
- Replacing by (2) and (3), we get:

- Simplifying and rearranging terms, we can solve for h (height required) as follows:
