Question

A toy car mass 0.05 kg ,on a ramp with no friction , begins at 0.7 meters high. At the bottom it collides inelastically with a toy truck mass 0.2 kg, at rest.  After the collision the car is at rest, what is the final velocity of the truck?

Answer 1

Ke of toy car =(1/2) m v^2 = m g h
so
v = sqrt(2gh) = sqrt(2*9.81*0.7)
v = 3.71 m/s
momentum = 0.05*v = 0.185 kg m/s
so
0.2 u = 0.185
u = 0.926 m/s

Answer 2

V^2 = Vo^2 + 2g*h.
V^2 = 0 + 19.6*0.7 = 13.72
V = 3.7 m/s = Velocity at the bottom of the ramp.

M1*V1 + M2*V2 = M1*0 + M2*V.
0.05*3.7 + M2*0 = 0 + 0.2V
0.185 = 0.2V
V = 0.925m/s = Final velocity of the truck.