A baseball (m = 150 g) approaches a bat horizontally at a speed of 40.5 m/s (90.6 mph) and is hit straight back at a speed of 46.9 m/s (105 mph).

Question

If the ball is in contact with the bat for a time of 1.25 ms, what is the average force exerted on the ball by the bat? Neglect the weight of the ball, since it is so much less than the force of the bat. Choose the direction of the incoming ball as the positive direction.

Answer 1

Use the impulse equation (a form of Newton's 2nd Law): FΔt = Δ(mv) where Δ means "change in"

The change in momentum is m_BB(v_f - v_i) = (.150 kg)(-46.9 m/s - 40.5 m/s)

Divide this by the time interval and you get F exerted by the bat in Newtons.

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