# Practice problems - Rolling, Torque , and Angular Momentum

Rolling, Torque , and Angular Momentum

1. A constant horizontal force of magnitude 10 N is applied to a wheel of mass 10 kg and radius 0.30 m as shown in the figure below. The wheel rolls smoothly on the horizontal surface and the acceleration of its center of mass has magnitude 0.60 m/s^2. ( a) what are the magnitude and direction of the frictional force on the wheel ?

2. Two particles , each of mass m and speed v , travel in opposite directions along parallel lined separated by a distance d. (a) In terms of m, v and d , find an expression for the magnitude L of the angular momentum of the two-particle system around a point midway between the two lines. (b) Does the expression change if the point about which L is calculated is not midway between the lines? (c) Now reverse the direction of travel for one of the particles and repeat (a) and (b)

3. A uniform thin rod of length 0.50m and mass 4.0 kg can rotate in a horizontal plane about a vertical axis through its center. The rod is at rest when a 3.0 g bullet traveling in the horizontal plane of the rod is fired into one end of the rod. As viewed from above the direction of the bullets velocity makes an angle of 60 degrees with the rod (figure below). If the bullet lodges in the rod and the angular velocity of the rod is 10 radians per second immediately after the collision, what is the bullets speed just before impact?

4. (figure below ) A uniform rod (length = 0.60 meters, mass = 1.0 kg ) rotates about and axis through one end with a rotational inertia of 0.12 kg * m^2 . As the rod swings through its lowest position, the end of the rod collides with a small 0.20 kg putty wad that sticks to the end of the rod. If the angular speed of the rod just before the collision is 2.4 radians per second, what is the angular speed of the rod-putty system immediately after the collision?

5. At the instant the displacement of a 2.00 kg object relative to the origin is vector d = ( 2.00 m ) + (4.00 m) - (3.00 m) , its velocity is

vector v = -(6.00m/s) + (3.00m/s) + (3.00m/s) , and it is subject to a force vector F= (6.00 N) - (8.00 N) + (4.00 N) . Find (a) the acceleration of the object, (b) the angular momentum of the object about the origin , (c) the torque about the origin acting on the object , and (d) the angle between the velocity of the object and the force acting on the object.

6. A uniform solid ball rolls smoothly along a floor , then up a ramp at 15 degree's. It momentarily stops when it has rolled 1.50 m along the ramp. What was its initial speed ?

#### Solution Summary

A set of 6 parctice problems. The solution gives all steps along with proper explanations so that you can solve similar problems yourself.