# physics

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Will check my work and help me with the last two problems please?

A 4 kg ball has a momentum of 12 kg m/s. What is the ball's speed?
-(12 kg/m/s) / 4kg=3m/s

A ball is moving at 4 m/s and has a momentum of 48 kg m/s. What is the ball's mass?
-(48kg/m/s) / (4m/s) =12 kg

A 1-kg chunk of putty moving at 1 m/s collides with and sticks to a 5-kg bowling ball initially at rest. The bowling ball and putty then move with a momentum of? (This one I don't know how to work)

A 1000-kg car moving at 10 m/s brakes to a stop in 5 s. The average braking force is? (This one I don't know how to work)

• physics -

on the fourth: comentum is conserved, final momentum is = initial momentum.

on the last:
vf^2=vi^2+force*distance

where distance is average velocity*time or
(vf+vi)/2 * t

solve for force

first two correct.

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