1. Torque is used to determine the weight of an object. A 10 m long pole, weighing 20 N, has its center of gravity 2 m from one end. An object of unknown weight is hung at the end opposite the center of gravity. With the object hanging at this end, the pole now balances 2 m from the unknown weight. What is the weight of the unknown weight? Ans: 60 N
2. A tapered log 5 m long has its center of gravity 1 m from the thick end. It weighs 20 N. Where must a 30 N weight be hung in order to balance it at its center? Ans: 1 m from center
3. A 10 m long pole balances at its center. A 20 N force is applied upward at one end. A 35 N weight is hung 3 m from this 20 N force. A 40 N force is applied upward at the other end. What is the magnitude of the unknown weight that is hanging 2 m from the 40 N force that causes equilibrium? Ans: 56.67 N
4. A uniform, hinged beam, weighing 20 N and 8 m long is attached to a wall. A 100 N weight is hung at the free end. A rope is attached to beam 2 m from the free end. If the rope is attached perpendicular to the ceiling and to the beam, what is the tension in the rope? Ans: 146.67 N
5. Now the rope in number 4 is attached at an angle of 20° to the ceiling. What is the tension in the rope? Ans: 428.82 N
6. Two men, A and B, carry a 3 m massless pole with its ends horizontally on their shoulders. A 480 N weight is hung on the pole 1 m from A. A 320 N weight is hung on the pole 0.6 m from B. How much weight is carried by each man? Ans: 384 N; 416 N
7. A tapered log, 15 long and weighing 300 lb, has its center of gravity 5 ft from the thick end. The log is supported at its ends. A 150 lb weight is hung from the log 3 ft from its thin end. How much force must be exerted by each of the end supports? Ans: 230 lb; 220 lb
8. A 100 N force is applied at the end of a massless pole 3 m long. It is applied at an angle of 30° to the pole. What is the torque produced? Ans: 150 N m

Torque and Rotational Motion Notes

Torque and Rotational Motion Sample Problems

Rotational Motion Homework