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 drawing shows a lower leg being exercised. It has a 49-N
weight attached to the foot and is extended at an angle 0 with
respect to the vertical. Consider a rotational axis at the knee. (a) When
0 = 90.0°, find the magnitude of the torque that the weight creates. (b) At
what angle 0 does the magnitude of the torque equal 15 N · m?
69.
Axis
0.55 m
49 N
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 model airplane with mass 0.757 kg is tethered to the ground by a wire so that it flies in a horizontal circle 29.0 m in radius. The airplane engine provides a net thrust of 0.810 N perpendicular to the tethering wire.
(a) Find the magnitude of the torque the net thrust produces about the center of the circle. N · m(b) Find the magnitude of the angular acceleration of the airplane. rad/s2(c) Find the magnitude of the translational acceleration of the airplane tangent to its flight path.
Chapter 11 Solutions
University Physics with Modern Physics (14th Edition)
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