AP Physics Chapter 11-12 Key Equations and Ideas Practice
1. A 10.0-kg flywheel with a radius of 0.250 m has an initial angular speed of 144 radians per second.
The brakes are applied and the flywheel slows at a rate of 6.00 radians per second squared.
A. How much kinetic energy does the flywheel initially have?
B. How long does it take for the flywheel to come to a stop?
C. How many radians does the flywheel turn through before it comes to a stop?
D. How far does a point on the rim of the flywheel travel before it comes to a stop?
E. What is the radial acceleration at a point 0.150 m from the center of the flywheel at t = 10.0 s?
In what direction does it point?
F. What is the applied torque causing the flywheel to stop?
2. Disk
A. What is the rotational inertia of a disk when the rotational axis passes through its center?
B. What is the rotational inertia of a disk when the rotational axis is on the rim of the disk?
3. A 7.00 kg mass is attached to a 2.00 kg mass by a massless rod. The center of masses are 2.00 m
apart. If this system is tossed in the air spinning, how far from the 7.00-kg mass is the center of
rotation?
4. A 4.00 kg hoop with a radius of 0.200 m is placed at the top of an incline. The hoop descends a
vertical distance of 1.00 m.
A. If the incline is frictionless, what is the linear speed of the hoop at the bottom of the incline?
B. If the incline has friction and the hoop rolls without slipping, what is the linear speed at the
bottom of the ramp?
C.
If the incline has friction and the hoop rolls without slipping, what is the rotational rate of the
hoop at the bottom of the ramp?
5. If a net torque of 9.00 N m is applied to 5.00-kg solid sphere with a radius of 0.300 m, what is the
rate of change of angular momentum of the sphere with respect to time?
Solutions:
1. A. 3.24 x 103 J
2. A. ½MR2
4. A. 4.43 m/s
B. 24 s
C. 1.73 x 103 rad
B. 3/2 MR2
B. 3.13 m/s
D. 432 m
E. 1.06 x 103 m/s2
3. 0.444 m
C. 15.7 rad/s
5. 9.00 N m
F. 1.88 N m