a roller coaster at an amusement park is at rest of top of a 30m hill (point A). the car starts to roll down the hill and reaches (point b), which is 10 m above the ground, and then rolls up the track to point C, which is 20 m above the ground.

- A student assumes no energy is lost, and solves for how fast is the car moving at point C using energy arguements. What answer does he get?

Question

a roller coaster at an amusement park is at rest of top of a 30m hill (point A). the car starts to roll down the hill and reaches (point b), which is 10 m above the ground, and then rolls up the track to point C, which is 20 m above  the ground. 

- A student assumes no energy is lost, and solves for how fast is the car moving at point C using energy arguements. What answer does he get?

anonymous · Answer

it will be much easier if u show the diagram

anonymous · Answer

You just need to use the mechanical energy conservation conservation.

As c is located 10m below a . So the potential energy lost will be "mgh"  where h=10m.
This is converted into kinetic energy at c. As initially there was no kinetic energy with the body and suppose the velocity at c is "v"

Then       mgh = mv^2/2