BIO TORQUES AND TUG-OF-WAR. In a study of the biomechanics of the tug-of-war, a 2.0-m-tall, 80.0-kg competitor in the middle of the line is considered to be a rigid body leaning back at an angle of 30.0° to the vertical. The competitor is pulling on a rope that is held horizontal a distance of 1.5 m from his feet (as measured along the line of the body). At the moment shown in the figure, the man is stationary and the tension in the rope in front of him is T 1 = 1160 N. Since there is friction between the rope and his hands, the tension in the rope behind him, T 2, is not equal to T 1 . His center of mass is halfway between his feet and the top of his head. The coefficient of static friction between his feet and the ground is 0.65. 11.95 His body is leaning back at 30.0° to the vertical, but the coefficient of static friction between his feet and the ground is suddenly reduced to 0.50. What will happen? (a) His entire body will accelerate forward; (b) his feet will slip forward; (c) his feet will slip backward; (d) his feet will not slip.
BIO TORQUES AND TUG-OF-WAR. In a study of the biomechanics of the tug-of-war, a 2.0-m-tall, 80.0-kg competitor in the middle of the line is considered to be a rigid body leaning back at an angle of 30.0° to the vertical. The competitor is pulling on a rope that is held horizontal a distance of 1.5 m from his feet (as measured along the line of the body). At the moment shown in the figure, the man is stationary and the tension in the rope in front of him is T 1 = 1160 N. Since there is friction between the rope and his hands, the tension in the rope behind him, T 2, is not equal to T 1 . His center of mass is halfway between his feet and the top of his head. The coefficient of static friction between his feet and the ground is 0.65. 11.95 His body is leaning back at 30.0° to the vertical, but the coefficient of static friction between his feet and the ground is suddenly reduced to 0.50. What will happen? (a) His entire body will accelerate forward; (b) his feet will slip forward; (c) his feet will slip backward; (d) his feet will not slip.
BIO TORQUES AND TUG-OF-WAR. In a study of the biomechanics of the tug-of-war, a 2.0-m-tall, 80.0-kg competitor in the middle of the line is considered to be a rigid body leaning back at an angle of 30.0° to the vertical. The competitor is pulling on a rope that is held horizontal a distance of 1.5 m from his feet (as measured along the line of the body). At the moment shown in the figure, the man is stationary and the tension in the rope in front of him is T1 = 1160 N. Since there is friction between the rope and his hands, the tension in the rope behind him, T2, is not equal to T1. His center of mass is halfway between his feet and the top of his head. The coefficient of static friction between his feet and the ground is 0.65.
11.95 His body is leaning back at 30.0° to the vertical, but the coefficient of static friction between his feet and the ground is suddenly reduced to 0.50. What will happen? (a) His entire body will accelerate forward; (b) his feet will slip forward; (c) his feet will slip backward; (d) his feet will not slip.
The 100 kg skier’s knee can withstand a lateral torque of 500 N∙m before dislocating. As the skier loses control going around a corner, one ski comes up off the snow and the other boot and lower leg remain vertical, such that the knee starts to bend laterally. If the distance from the skier’s knee to his center of mass is 1 m, at what angle θ from vertical will the knee dislocate due to the torque of gravity alone?
a) 30 degrees
b) 45 degrees
c) 60 degrees
d) 90 degrees
Athletes sometimes do an exercise called “curling weights”. This exercise consists of holding the arm steady from the shoulder to the elbow while pulling a weight to the chest. Calculate the torque about the elbow caused by a 40.0-pound weight that makes an angle of 55.0 degrees with respect to the body.
A man in a gym is holding an 8.0-kg kettlebell at arm's length, a distance of 0.55 m from his shoulder joint. What is the torque about his shoulder joint due to the gravitational force on the kettlebell if his arm is held at 30° below the horizontal?
Chapter 11 Solutions
University Physics with Modern Physics, Volume 2 (Chs. 21-37); Mastering Physics with Pearson eText -- ValuePack Access Card (14th Edition)
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