Question

That neighbor's pesky kid now has new missiles that make elastic collisions.

He insists on throwing 25.0 g rocks at your new 2.25 kg light fixture hanging by a 26.0 cm wire from the ceiling of your porch. If each rock strikes the fixture traveling at 10.0 m/s, how high will the light fixture go after it is hit by one of these new missiles?

h = ___ m

I got .057 m but it is incorrect.

Answer 1

You have to figure the velocity of the light fixture at collision time.
Use conservation of energy, and conservation of momentum.

Once you get the intial velocity of the light fixture,

1/2 masslight*velocitylight^2=masslight*g*height and solve for h