Roller coaster work gravitational energy.

[tebes]

Homework Statement

a frictionless roller coaster car of mass m = 954 kg tops the first hill with speed v0 = 24.2 m/s at height h = 30.8 m. How much work does the gravitational force do on the car from that point to (a) point A. (same height)

Homework Equations

The Attempt at a Solution

One question is baffling me, do I need to include kinetic energy when calculating using the change of gravitational potential energy? Does it mean that question (a), work does by the gravitational force is zero ?

 

[Doc Al]

One question is baffling me, do I need to include kinetic energy when calculating using the change of gravitational potential energy?

No.

Does it mean that question (a), work does by the gravitational force is zero ?

That's what I would say. Going from one point to another of equal height, the change in gravitational PE (and thus the work done by gravity) is zero.