The length of a bicycle pedal arm is 0.165 m, and a downward force of 149 N is applied to the pedal by the rider. What is the magnitude of the torque about the pedal arm's pivot when the arm is at an angle of (a)42.8°, (b) 90°, and (c) 180° with the vertical?

If you and your friend are sitting on a seesaw and their masses are 60 kg and 80 kg, (a) how far you have to sit from the center of seesaw to balance it if your friend is sitting at 30 cm from the center on other side?  (b) What are torques created by each of you? What are the directions of torque?

A force F=(-5j+3k)N is applied to an object that is a distance r=(2j+6k)m from a pivot point.  (a) Calculate the torque on the object.(b) Calculate the angle between r and F.

Two forces, F1=100 N (Newton) and F2=20N, are applied on opposite sides of a door's knob at angles theta_1=30 degrees and theta_2=60 degrees respectively, causing the door to rotate (about the axis passing though its hinges). If the distance from the knob to the rotation axis is 0.8 meter, find the net torque exerted on the door and specify the direction of rotation of the door (in this problem, assume that the force F1 causes a counterclockwise rotation and F2 a clockwise rotation). A.) Net Torque = 26.14 N.m; the door rotates counterclockwise. B.) Net Torque = -25.4 N.m; the door rotates counterclockwise. C.) Net Torque = 123.8 N.m; the door rotates clockwise. D.) Net Torque = 1.784 N.m; the door rotates clockwise.