An athlete with a mass of 450 kg is doing pushups as shown i

An athlete with a mass of 45.0 kg is doing pushups as shown in the figure below. The value for

r_W

is 0.80 m and the value for

r_R

is 1.48 m.

(a) Assuming she moves upward at a constant speed, determine the force she must exert on the floor with each hand to do a push-up.
  N

(b) The triceps muscle in the back of her upper arm with an effective lever arm of

r_T = 1.70 cm,

as shown in the figure below, and she exerts force on the floor a horizontal distance of

r\'_R = 2.05 cm

from the elbow joint.

Determine the force in the triceps muscle.
N

In order to appreciate the strength of the triceps, determine the ratio of the force in the tricep muscle to her weight (in decimal form).

(FT/W)=

I would love to see your work as to how you got the answers. Thank you!

=

Solution

lif we assume F as the force exerts on each hand

then usning Balancing Condtion SUm of Forces = 0

2*F*1.48 - 46*9.8 * 0.8= 0

F = 121.83 N
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b) using the Balancing moment about elbow ,

Ft * 1.48 - 121.83 *2.05 = 0

Ft = 168.7 N

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For Ft/W = 168.7.1/(45*9.8)

Ft/W = 0.382