To strengthen his arm and chest muscles, an 79.0kg athlete 2.00m tall is doing a

Question

To strengthen his arm and chest muscles, an 79.0kg athlete 2.00m tall is doing a series of push-ups as shown in the figure below (Figure 1) . His center of mass is 1.15m from the bottom of his feet, and the centers of his palms are 30.0cm from the top of his head. Find the force that the floor exerts on each of his feet and on each hand, assuming that both feet exert the same force and both palms do likewise.

(Figure 1.)

Part A:

Find the force that the floor exerts on each of his feet, assuming that both feet exert the same force.

Part B:

Find the force that the floor exerts on each of his hand, both palms exert the same force.

Explanation / Answer

Let F_feet is the force exrted by floor on each feet and

F_palm is the force exerted by floor on each palm.

As the person is in equilibrium net force and net torque abot any point is zero.

A)
net Torque about palm = 0

79*9.8*(0.85-0.3) - 2*F_feet*1.7 = 0

F_feet = 79*9.8*(0.85-0.3)/(2*1.7)

= 125.24 N <<<<<<<<<<<<<<<<<<<----------Answer

B)
net Torque about feet = 0

2*F_palm*1.7 - 79*9.8*1.15 = 0

F_palm = 79*9.8*1.15/(2*1.7)

= 261.86 N <<<<<<<<<<<<<<<<<<<----------Answer

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