Answer:
She used a device to fire tennis balls at a mannequin head.
Explanation: EXACT ANSWER FROM PLATO/EDMENTUM!!! <3
Naya used a machine that shoots tennis balls, like this one, to fire balls at a mannequin's head. ... Once Naya knew how much the mannequin moved with each hit, she could calculate how much force the head had received from each blow.
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