To strengthen his arm and chest muscles, an 77.0 kg athlete 2.00 m tall is doing

Question

To strengthen his arm and chest muscles, an 77.0 kg athlete 2.00 m tall is doing a series of push-ups as shown in the figure below (Figure 1) . His center of mass is 1.15 m from the bottom of his feet, and the centers of his palms are 30.0 cm 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

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

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

Explanation / Answer

a)

As the person is in equilibrium net force and net torque acting on him must be zero.

Apply net torque about palms = 0

77*9.8*(2 - 1.15 - 0.3) - 2*F_feet*(2 - 0.3) = 0

F_feet = 77*9.8*(2 - 1.15 - 0.3)/(2*(2 - 0.3))

= 122 N

b)

apply net torque about feets = 0

77*9.8*1.15 - 2*F_palm*(2 - 0.3) = 0

F_palm = 77*9.8*1.15/(2*(2 - 0.3))

= 255.2 N

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