College Physics
1st Edition
ISBN: 9781938168000
Author: Paul Peter Urone, Roger Hinrichs
Publisher: OpenStax College
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Chapter 9, Problem 27PE
Two muscles in the back of the leg pull on the Achilles tendon as shown in Figure 9.37. What total force do they exert?
Figure 9.37 The Achilles tendon of the posterior leg serves to attach plantaris, gastrocnemius, and soleus muscles to calcaneus bone.
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A person places his hand palm downward
on a scale and pushes down on the scale
until it reads 96.0 N. The triceps muscle is
responsible for this arm extension force.
Find the force exerted by the triceps
muscle. The bottom of the triceps muscle
is 2.50 cm to the left of the elbow joint,
and the palm is pushing at approximately
29.0 cm to the right of the elbow joint.
P
96.0 N
2.50 cm and Q = 29.0 cm.
where P =
When you bend your knee, the quadriceps muscle is stretched. This increases the tension in the quadriceps tendon attached to your kneecap (patella), which, in turn, increases the tension in the patella tendon that attaches your kneecap to your lower leg bone (tibia). Simultaneously, the end of your upper leg bone (femur) pushes outward on the patella. Shown is how these parts of a knee joint are arranged. What size force does the femur exert on the kneecap if the tendons are oriented as in the figure and the tension in each tendon is 60 N?
Unlike most of the other muscles in our bodies, the masseter muscle in the jaw, as illustrated in the figure, is attached relatively far from the joint, enabling very large forces to be
exerted by the back teeth. This is shown in the figure below, where a person is biting down on a bullet placed between the back teeth. (F, = 320 N and r, = 4.7 cm.)
= 2.9 cm
M
Masseter
muscle
reaction
(a) Using the information in the figure, calculate the magnitude of the force exerted by the teeth on the bullet.
(b) Calculate magnitude of the force on the joint.
N
Chapter 9 Solutions
College Physics
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