Posted by **Anonymous** on Sunday, January 2, 2011 at 5:47pm.

A child and sled with a combined mass of 40.0 kg slide down a frictionless hill. If the sled starts from rest and has a speed of 9.0 m/s at the bottom, what is the height of the hill?

m

- physics -
**Marth**, Sunday, January 2, 2011 at 6:24pm
Use energy:

gravitational potential energy: GPE = mgh

kinetic energy: KE = (1/2)m*v^2

By conservation of energy, GPEi+KEi = GPEf + KEf. (Final energy = initial energy).

At the bottom of the hill, GPEf = 0 (h=0). At the top of the hill, KEi = 0(v=0). Find the final kinetic energy, and from it, the final velocity.

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