Two ice skaters push off against one another starting from a stationary position. The 45-kg skater acquires a speed of 0.375 m/s. What speed does the 60-kg skater acquire?
A) 0.500 m/s
B) 0.281 m/s
C) 0.375 m/s
D) 0.750 m/s
E) 0 m/s

Question

Quizplus · Accepted Answer

From conservation of momentum, we know that the total momentum before the push-off is zero. After the push-off, the momentum is still zero. Let the velocity of the 60-kg skater be v. Therefore, we have:
(45 kg)(0.375 m/s) + (60 kg)(v) = 0
v = - (45/60)(0.375) = -0.28125 m/s
Since the 60-kg skater acquires a velocity in the opposite direction, the magnitude of the velocity is 0.281 m/s. Therefore, the best choice is B.

Two Ice Skaters Push Off Against One Another Starting from a Stationary