Physics (momentum and inelastic collision)?

Question

A 60 kg ice skater moving to the right with a velocity of 3m/s throws a 0.150 kg snowball to the right with a velocity of 30m/s relative to the ground.
What is the velocity of the ice skater after throwing the snowball? Disregard the friction between the skates and the ice. Answer in units of m/s.
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A second skater initially at rest with a mass of 58kg catches the snowball.
What is the velocity of the second skater after catching the snowball in a perfectly inelastic collision? Answer in units of m/s


Help on this would be much appreciated, thanks in advance!!!

Answer 1

Linear momentum is conserved, so the initial momentum of the system is equal to the final momentum.

Initial momentum:

(60 kg + .150 kg)(30 m/s)

Final momentum:

(60 kg) (v) + (.150 kg)(30 m/s)

Set these expressions equal and solve for v, the final velocity of the skater. It will be very nearly 3 m/s.

The same technique works for the second part.

The initial momentum is

(.150 kg)(30 m/s)

The final momentum is

(58 kg + .150 kg)(v)

Set these expressions equal and solve for v. It will be very small.

If this problem is from a textbook, complain. You're given a number of parameters with only one significant figure (60 kg, 30 m/s) and asked to compute velocities with several significant figures. In fact, to the number of significant figures given, the answer to the first part is 30 m/s and the answer to the second part is zero.