problems on curved mtion

[Clari]

A frictionless roller coaster of mas m starts at point A with speed v0. Assume that the roller coaster can be considered as a point particle and that it always remains on the track.

a.) what will be the speed of the roller coaster at point B and C?

P.S.: A and B are both ( h ) unit from the ground, and C is h/2 from the ground, and D is on the ground...B is xy unit from A, and C is xy unit from B too...and yz unit is D from C


Can someone please help me with me? Thank you~

[arildno]

Mechanical energy is conserved.
What does that mean?

[Clari]

oh, yes..I get it now...Thank you Arildno...^-^

[Clari]

For part c of this question: suppose v0 = 0, how long will it take the roller coaster to reach point B?

I have no idea how to answer it...>_< Please help.