College Physics
1st Edition
ISBN: 9781938168048
Author: Paul Peter Urone, OpenStax, Roger Hinrichs
Publisher: OpenStax
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Textbook Question
Chapter 9, Problem 12CQ
Explain why the forces in our joints are several times larger than the forces we exert on the outside world with our limbs. Can these forces be even greater than muscle forces (see previous Question)?
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Question 1) The figure shows a person wearing weight boots and doing lower leg flexion/extension exercise in sitting
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Chapter 9 Solutions
College Physics
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.Similar questions
- 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. (FM = 295 N and rR = 4.0 cm.) (a) Using the information in the figure, calculate the magnitude of the force exerted by the teeth on the bullet._________ N(b) Calculate magnitude of the force on the joint._________ Narrow_forwardA hand exerts a force of 25 lbs on a scale at 16 inches from the joint center at the elbow. If the triceps attach to the ulna at a 90° angle and at a distance of 2.5 cm from the elbow joint center, and if the weight of the forearm and hand is 12 lbs with the hand/forearm CG located 15 cm from the elbow joint center, how much force is being exerted by the triceps? 880 1488 N 8800 O 15.640 N Onone of the answers are correctarrow_forwardUnlike 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. Narrow_forward
- Unlike most of the other muscles in our bodies, the masseter muscle in the jaw, as illustrated in as shown, is attached relatively far from the joint, enabling large forces to be exerted by the back teeth. (a) Using the information in the figure, calculate the force exerted by the lower teeth on the bullet. (b) Calculate the force on the joint.arrow_forwardThere is a small but appreciable amount of elastic hysteresis in the large tendon at the back of a horse’s leg. Explain how this can cause damage to the tendon if a horse runs too hard for too long a time.arrow_forwardWhen just a single force is present, can an item be in equilibrium? Explain.arrow_forward
- In the figure below, the biceps muscle exerts a force supporting a perpendicular forearm and a book. Suppose we replace the book with an elastic exercise rope that obeys Hooke's Law. Assume its force constant k = 453 N/m. Triceps muscle Biceps U muscle PHYSICS m, = 4.3 kg CG FE m, = 3.7 kg Wo CG 4.0 cml Wa 16 cm 38 cm (a) How much is the rope stretched (past equilibrium) to provide the same force w, as before the book was replaced? Assume the rope is held in the hand at the same location as the book. (Enter your answer in cm.) |cm (b) What force (in N) is on the biceps muscle if the exercise rope is pulled straight up so that the forearm makes an angle of 18° with the horizontal? Assume the biceps muscle is still perpendicular to the forearm. (Assume the same stretch in the rope as part (a). Enter the magnitude.)arrow_forwardIf the elbow was flexed to 135°, would the internal force required by the biceps brachii be greater than or less than the force when the elbow was flexed to 90°? Why?arrow_forwardDuring most of the stance phase of the gait, the knee flexion is less than 20º. What force must the quadriceps muscle apply to maintain this flexion while standing on one leg? The patient's weight is 836N, assuming that the distance from the center of the joint to the line of gravity is 5 cm and the distance perpendicular to the center of the joint towards which the muscle acts is 5 cm, and the muscle acts ( pull) at 60º to the horizontal.arrow_forward
- When you lift an object by moving only your forearm, the main lifting muscle in your arm is the biceps. Suppose the mass of a forearm is 1.10 kg . If the biceps is connected to the forearm a distance dbicepsdbicepsd_biceps = 2.50 cm from the elbow, how much force Fbiceps must the biceps exert to hold a 750 g ball at the end of the forearm at distance dball = 32.0 cm from the elbow, with the forearm parallel to the floor? Although it is uncommon, orthopedic surgeons have seen patients who have torn their biceps tendon when forces of greater than 390 N have been exerted on the tendon with the arm bent at the elbow so that the forearm is parallel to the ground. What is the minimum mass of a ball Mball such a patient might have held to cause the biceps tendon to tear?arrow_forwardWhen 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?arrow_forwardWhen you carry a heavy load with one arm, why do you tend to hold your free arm away from your body?arrow_forward
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