Question

Consider hitting someone with a Wiffle ball bat. Will it hurt them more if you grab the end or the middle of the bat when you swing it? Explain your thinking, but do so using the vocabulary of moment of inertia (treat the bat as a rod) and torque (in this case, torques caused by the contact forces the other person’s head and the bat are exerting on each other).

Answer 1

Grabbing the end of wiffle ball bat will hurt more because if we grab it from the end , the effective length of bat is maximum and hence on applying a little force , a large torque will be exerted . It is because, torque = r × F .

Also , torque is a function of moment of inertia and this when we grab the bat from end , the moment of inertia increase and thus hitting more strongly.

It can also be compared with the levers . Levers are provided with long arms, so that on applying small forces , we can easily open the hard stuck nuts and bolts .

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