Worksheet 11A

Physics
Name
Dec. 12, 2008
WS 11A: Torque
1. Is the use of the rope increasing the torque exerted on the stuck nut Please
explain.
2. When you open a door, you typically exert two torques.
For each torque, draw a picture with the force and lever arm clearly labeled.
3. To loosen the lid on a jar of jam 9.0 cm in diameter a torque of 9 N·m must be applied to
the circumference of the lid.
(a) How much force must be applied if you grab the lid with your hand
(b) If a jar wrench whose handle extends 15 cm from the center of the jar is attached to
the lid, what is the minimum force required to open the jar
4. Describe an original situation where you see a torque being exerted. Sketch it (clearly indicate the rotation
point, the lever arm distance, the point where the force is being applied, and the resulting direction of
rotation).

5. Calculate the net torque about the axle of the wheel shown at right. Besides
the three forces shown in the picture, there is a fourth torque, caused by
friction which exerts a torque of 0.4 Nm in a direction that opposes the motion.
FROM THE TEXT:
C.2 (a) Can an object have an angular velocity if there is no net torque acting on it (b) Can an object have a net
torque acting on it if it has zero angular velocity Explain!
2.1 A 3.30 kg birdfeeder hangs from the tip of a 1.10 m pole that sticks up from the ground at a 65.0° angle.
What is the magnitude of the torque exerted on the pole by the birdfeeder Treat the bottom end of the pole
as the pivot point. Sketch the problem too.
2.4 A straight 2.60 m rod pivots around a vertical axis
so that it can swing freely in a horizontal plane.
Jane pushes perpendicular to the rod at its
midpoint with 98.0 N of force, directed
horizontally, to create a torque. Matt has
attached a rope to the end of the rod, and is
pulling on it horizontally to create an opposing
torque. The rope creates a 67.0° angle with the
rod. With what force should Matt pull so that the
net torque on the rod is zero