A 7.0-kg bowling ball strikes a 2.0-kg pin.The pin flies forward with a velocity of 6.0 m/s;the ball continues forward at 4.0 m/s.What was the original velocity of the ball?

Question

Quizplus · Accepted Answer

We can use the conservation of momentum to solve this problem.

Initial momentum = Final momentum

m_ball * v_initial = m_ball * v_ball_final + m_pin * v_pin_final

where
m_ball = 7.0 kg (mass of the ball)
m_pin = 2.0 kg (mass of the pin)
v_ball_final = 4.0 m/s (final velocity of the ball)
v_pin_final = 6.0 m/s (final velocity of the pin)

Rearranging the equation, we get

v_initial = (m_ball * v_ball_final + m_pin * v_pin_final)/m_ball

v_initial = (7.0 kg * 4.0 m/s + 2.0 kg * 6.0 m/s)/7.0 kg

v_initial = 5.7 m/s

Therefore, the original velocity of the ball was 5.7 m/s, which is choice B.

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