Problem 5.18: Force during a jump. A person reaches a maximum height of 64 cm wh

Question

Problem 5.18: Force during a jump. A person reaches a maximum height of 64 cm when jumping straight up from a crouched position. During the jump itself, the person's body from the knees up rises a distance of around 43 cm To keep the calculations simple and yet get a reasonable result, assume that the entire body rises this much during the jump. Part A With what initial speed does the person leave the ground to reach a height of 64 cm Express your answer using two significant figures. 35 m/s Submit My Answers Give Up Correct Part B In terms of this jumper's weight W.what force does the ground exerton him or her during the jump? Express your answer using two significant figures. F. 1.90 Submit My Answers Give Up incorrect: Try Again: 5 attempts remaining

Explanation / Answer

part A:

initial velocity required=sqrt(2*g*height)

=sqrt(2*9.8*0.64)

=3.5418 m/s

part B:

let acceleration of the body is a m/s^2.

initial speed=3.5418 m/s

final speed=0 m/s

height=0.43 m

then acceleration=(final speed^2-initial speed^2)/(2*distance)

=(0^2-3.5418^2)/(2*0.43)

=-14.586 m/s^2
magnitude of acceleration in terms of g=14.586/9.8=1.4884*g

then force applied by the ground=mass * acceleration

=1.4884*W

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