Torque and Rotations Review
1. Find the moment of inertia of a 200. gram saw blade that is 30. cm in diameter. (refer to handout for I formulas)
b) What angular acceleration will result if the blade is acted upon by a 10. Nm torque?
2. A pitcher throws a ball by rotating his arm around his shoulder joint. If the ball is 0.050 kg and his arm is 5.0 kg and 0.80 m long, what torque is required of the shoulder to accelerate the arm at 25 rad/s2? Assume the arm is a solid rod and the ball is a pt. mass, where I = Irod + Ipt. mass. (Refer to your handout for I formulas)
3. A string is wound around the flywheel of a motor that is 20 cm in diameter. If a boy pulls the string with 40 N of force, what torque will he produce?
b) What angular acceleration will he produce if the flywheel is a solid disc with mass=2 kg? (Refer to your handout to I formulas)
4. A 10m Teeter-Totter is balanced at its center. Mr. Stratton (100kg) is sitting 3m from the center and Mrs. Stratton (50kg) is sitting at the very end on the other side, 5m from the center. Critter the dog (25kg) is to be placed on the Teeter-Totter to make it all balanced. How far from the center and in which direction (toward Mr. or Mrs. Stratton) should Critter be placed?
5. The following shapes have equal mass and are raced down a ramp. List them in the order they should finish.
Solid cylinder Hollow Cylinder Solid Sphere
1st place______2nd place______3rd place______
6. Find the force (F) that will cause equilibrium in the see-saw. The beam has a mass of 5.0kg.
7. Find the torque about the axis indicated by the black circle.
a) b)
c) d)
8) A figure skater during her finale can increase her rotation rate from an initial rate of 1.6 rad/s seconds to a final rate of 9.4 rad/s.
a. If her initial moment of inertia was 4.6 kg·m2, what is her final moment of inertia?
b. Describe how she physically accomplish this change?
Answers:1) 2.25x10-3kgm2, 4,400 rad/s2 2) 27 Nm 3) 4 Nm 4) 2m from center, towards Mrs. Stratton 5) Solid Sphere, Solid Cyl., Hollow Cyl. 6) 12N 7) 5.6 Nm, 4.3 Nm, 11 Nm, 33 Nm 8) 0.78 kgm2, Bring her limbs in tight to body.