An athlete with a mass of 45.0 kg is doing pushups as shown in the figure below.
ID: 1458496 • Letter: A
Question
An athlete with a mass of 45.0 kg is doing pushups as shown in the figure below. The value for
rW
is 0.80 m and the value for
rR
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
rT = 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!
=
FT WExplanation / Answer
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
---------------------------------------
b) using the Balancing moment about elbow ,
Ft * 1.48 - 121.83 *2.05 = 0
Ft = 168.7 N
------------------------------------------
For Ft/W = 168.7.1/(45*9.8)
Ft/W = 0.382