![]() On the other side of the pivot an adult pushes straight down on the teeter-totter with a force of 95 N. Here, the center of mass is not accelerating, but the net torque is non-zero.Ĭhapter 11 Rotational Dynamics and Static Equilibrium Q.6PĪt the local playground, a 16-kg child sits on the end of a horizontal teeter-totter, 1.5 m from the pivot point. In both these cases the net force is zero. Give an example of a system in which the net force is zero but the net torqueis nonzero.Ĭonsider an airplane propeller or a ceiling fan that is just starting to rotate. Give an example of a system in which the net torque is zero but the net force is nonzero.Ī force applied radially to a wheel produces zero torque, though the net force is not zero.Ĭhapter 11 Rotational Dynamics and Static Equilibrium Q.5PĬhapter 11 Rotational Dynamics and Static Equilibrium Q.6CQ It follows that a given torque produces greater angular acceleration when the body rotates about an axis through the spine.Ĭhapter 11 Rotational Dynamics and Static Equilibrium Q.4PĬhapter 11 Rotational Dynamics and Static Equilibrium Q.5CQ This is true since the angular acceleration is inversely proportional to the moment of inertia. Therefore, rotating the body about an axis through the hips results in the larger moment of inertia. The moment of inertia is greatest when more mass is at a greater distance from the axis of rotation. Explain this behavior in terms of torques. When a motorcycle accelerates rapidly from a stop it sometimes “pops a wheelie” that is, its front wheel may lift off the ground. What torque does the trophy exert about the shoulder if the arm is (a) horizontal, or (b) at an angle of 22.5° below the horizontal?Ĭhapter 11 Rotational Dynamics and Static Equilibrium Q.4CQ Why?Ĭhapter 11 Rotational Dynamics and Static Equilibrium Q.3PĪ 1.61-kg bowling trophy is held at arm’s length, a distance of 0.605 m from the shoulder joint. Hence, the car pitches down in front when the brakes are applied sharply.Ĭhapter 11 Rotational Dynamics and Static Equilibrium Q.2PĬhapter 11 Rotational Dynamics and Static Equilibrium Q.3CQĪ tightrope walker uses a long pole to aid in balancing. The torque by gravity which is in the opposite direction to the torque by friction acts as the restoring torque because the first law of angular motion states that the body will maintain constant angular motion unless the outside torque is acted upon it. This clockwise rotation of the center of the mass causes the front of the car to pitch downward. The friction force opposes the motion and its direction is negative and this causes negative torque to be applied to the vehicle which leads to the clockwise rotation of the center of the mass as given by the expression of the torque. The total force on the car acts on the center of mass but the friction does not be applied on the center of mass of the vehicle and it is applied to the tires. When the brakes are applied, it causes the wheels to lock and then the friction plays the role to stop the car. Here, r is the distance of the axis of rotation to the force and F is the tangential force. Explain this observation in terms of torques. If a mechanic tightens the spark plug with a wrench that is 25 cm long, what is the minimum force necessary to create the desired torque?Ĭhapter 11 Rotational Dynamics and Static Equilibrium Q.2CQĪ car pitches down in front when the brakes are applied sharply. To tighten a spark plug, it is recommended that a torque of 15 N On the axis of rotationS A small force can produce the same torque as a large force, if it is applied farther from the axis of rotationĬhapter 11 Rotational Dynamics and Static Equilibrium Q.1P Here, the torque depends on both the magnitude of force and on the distance from the axis of rotation at which it is applied However because the forces are the same, the torque depends No, we know that the torque exerted by a tangential force a distance r from the axis of rotation ![]() Two forces produce the same torque Does it follow that they have the same magnitude? Explain Mastering Physics Solutions Chapter 11 Rotational Dynamics and Static EquilibriumĬhapter 11 Rotational Dynamics and Static Equilibrium Q.1CQ
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