1. What is the torque of a force of 10 N pushing a door open at a point 30 cm from its hinged edge if the force meets the door at an angle of 30.

2. Find the center of mass of three point masses arranged on the x axis: 3 kg at x=3, 2 kg at x=1 and 1 kg at x=-1

3. Find the center of mass of a circular plate of radius 10 cm if there is a perfect hole 4 cm in diameter drilled at the coordinates (2, 0). The origin is at the center of the platter.

4. Find the center of mass of the following masses at the indicated coordinates in meters: 3kg at (2,1); 5 kg at (-1,3); 8 kg at (-1,-1); and 4 kg at (0, 3).

5. Find the center of mass of the letter 'L' if it is made with both legs 1.0 m long and a width of 20 cm. The 'L' is made by placing the vertical segment on the floor (corner at 0,0) with edge also at (20,0), with the horizontal leg then starting from 20 cm and going until 1.2 m.

7. A solid ball () weighing 9.8 N and radius 10 cm is rotating at 3 rpm. What is its rotational energy? What is its angular momentum?

8. A solid ball () weighing 9.8 N and radius 10 cm is rolling at 3.0 m/s. What is its kinetic energy? What is its angular momentum?

9. A skater has a mass of 50 kg, and a moment of inertia of , and is rotating at 30 rpm. If the skater reduces her moment of inertia to , by retracting her arms, what is her new angular speed?

10. A skater of mass 50 kg, and a moment of inertia, and is rotating at 30 rpm. If the skater reduces her speed to 20 rpm, what is her new moment of inertia?

11. A marble of mass 0.100 kg is shot towards a stationary block at , and strikes the block 2 cm below its center of mass. What is the angular momentum of the block after the collision, if the marble returns with speed?

12. A solid ball ( ) of mass 0.5 kg is rolling down a ramp from a height 20 cm, how fast will it be rolling at the bottom of the ramp?

13. A solid ball ( ) of mass 2.0 kg is rolling at 5 m/s at the bottom of a ramp. If it started from rest, how high was the ramp?

14. A spring is compressed 25 cm and fires a 1.2 kg hoop ( ) rolling at a speed of 4.0 m/s. What is the stiffness of the spring?

15. What is the angular momentum of a solid ball spinning about its 5 cm radius at 20 rpm, if its mass is 1.3 kg? (). What is the kinetic energy ?

16. What is the kinetic energy of a solid ball rolling on the level floor, with a 5 cm radius, if its mass is 1.3 kg, and its linear speed on the ground is 3.0 m/s? ()

17. What is the minimum force necessary to give a cylinder of 10 cm radius, 40 cm high, and mass 4 kg, to turn on its axis with angular acceleration? I apply the force to the edge of the curved region of the cylinder ( ).