Question

when hit, the velocity of a 0.2 kg baseball changes from +25m/s to -25m/s. what is the magnitude of the impulse delivered by the bat to the ball?

Answer 1

Explanations & Calculations

• You can just apply the formula for the impulse to solve this question.
• Use the sign convention properly.

$\qquad\qquad \begin{aligned} \to(+)\\ \small I&=\small \Delta(mv)\\ &=\small m\Delta v\\ &=\small m[-v-(+v)]\\ &=\small -2mv\\ &=\small -2\times0.2\,kg\times25\,ms^{-1}\\ &=\small -10\,Nm \end{aligned}$

• Since the impulse gets a negative value along the previously considered direction, this means the impulse is otherway around: along the direction of the final velocity(back).