TP 8.30

Given:

m = 72.0 kg

v_i = 0

v_f = 1.20 m/s

W_nc1 = + 161 J

Find: W_nc2

Net work done on the athlete:

W_net = W_nc1 + W_nc2

On the other hand the work - kinetic energy theorem states that:

W_net =  K_f - K_i   = 1/2 mv_f² - 1/2 mv_i² =  1/2 mv_f²

W_nc1 + W_nc2 = 1/2 mv_f²

W_nc2 = - W_nc1 + 1/2 mv_f² =  - (161 J) + 1/2 (72.0 kg)(1.20 m/s)² = -109.16 J  = -109 J