posted by Emily .
A baseball player uses a pitching machine to
help him improve his batting average. He
places the 43.4 kg machine on a frozen pond.
The machine ﬁres a 0.0546 kg baseball horizontally at a speed of 44.8 m/s.
What is the magnitude of the recoil velocity
of the machine?
Answer in units of m/s
Let V be the recoil velocity. Since the total momentum must remain zero after throwing the ball,
0.0546*44.8 + 43.4*V = 0
V = -2.45/43.4 = -0.805 m/s
The minus sign means it moves in the opposite direction as the ball.