A boxer stops a punch with his head. To approximate the force ofthe blow, treat
ID: 1667961 • Letter: A
Question
A boxer stops a punch with his head. To approximate the force ofthe blow, treat the opponent's glove, hand, and forearm as aparticle of mass 1.68 kg moving with aninitial velocity of 21.5 m/s. (a) Estimate the force exerted on the head ifthe hand moves forward 8.0 cm whiledelivering the blow and then coming to rest.1 N
(b) Estimate the force exerted on the head if the head isdeliberately moved back during the punch so that the hand movesforward 16 cm while decelerating.
2 N (a) Estimate the force exerted on the head ifthe hand moves forward 8.0 cm whiledelivering the blow and then coming to rest.
1 N
(b) Estimate the force exerted on the head if the head isdeliberately moved back during the punch so that the hand movesforward 16 cm while decelerating.
2 N
Explanation / Answer
a ) A mass of a particle is m = 1.68kg moving with a initial velocity v0 = 21.5 m/s , travelled adistance is s = 8.0 cm = 0.08 m using Kinematic equation v2 -v02 = 2as ( 0m/s ) 2 - ( 21.5 m/s ) 2 = 2 a(0. 08m ) a = 2889 m/s2 Force exerted is F = ma = 1.68 kg * 2889 m/s2 = 4853 N b ) using Kinematicequation v2 - v02 =2as distance s = 16 cm = 0.16m ( 0m/s ) 2 - ( 21.5m/s ) 2 = 2 a(0. 16m ) a = 1444 m/s2 ThereforeF = m a = 1.68 * 1444 = 2427 N
Therefore
F = m a = 1.68 * 1444 = 2427 N
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