An athlete whose mass is 97.0 kg kg is performing weight-lifting exercises. Starting from the rest position, he lifts, with constant acceleration, a barbell that weighs 420 N N . He lifts the barbell a distance of 0.65 m m in a time of 1.5 s s . Part A Use Newton's laws to find the total force that his feet exert on the ground as he lifts the barbell. Express your answer using two significant figures. F floor Ffloor = nothing N?

470 N.

Explanation:

Using equations of motion:

S = vi*t + 1/2*(a*(t^2))

Given:

S = 0.65 m

t = 1.5 s

vi = 0 m/s

0.65 = 1/2 * (a * (1.5)^2)

a = 1.3/2.25

= 0.578 m/s^2

Force = mass * acceleration due to gravity

= 92 * 0.578

= 53.16 N

Total force = 420 + 53.16

= 473.16 N

= 470 N.

none, its a machine

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