Chapter 10/11

Chapter 10/11 – Rotational Kinematics and Energy/
Rotational Dynamics and Static Equilibrium
Ch10 - Pages: 301- 303
Ex: 16, 44, 60
Ch11 - Pages: 341-346
EX: 5, 8, 14, 20, 22, 52, 79
(Underlined ones are Torque and Eqilibrium Probs)
Chapter 10
16. After fixing a flat tire on a bicycle, you give the wheel a spin.
a. If the initial angular speed was 6.15 rad/s and it rotated 13.2 revolutions before coming to
rest, what was its average angular acceleration?
b. How long did the wheel rotate?
44. As you drive down the road at 17 m/s, you press on the gas pedal and speed up with a uniform
acceleration of 1.12 m/s2 for 0.65 s. If the tires on your car have a radius of 33 cm, what is their
angular displacement during this period of acceleration?
60. After you pick up a spare, your bowling ball rolls without
slipping back towards the ball rack with a linear speed of 2.85 m/s.
To reach the rack, the ball rolls up a ramp that rises through a
vertical distance of 0.53 m. What is the linear speed of the ball
when it reaches the top of the ramp?
Chapter 11
5. A person holds a 1.42-N baseball in his hand, a distance of 34.0
cm from the elbow joint. The biceps, attached at a distance of
2.75 cm from the elbow, exerts an upward force of 12.6 N on
the forearm. Consider the forearm and hand to be a uniform
rod with a mass of 1.20 kg.
a. Calculate the net torque acting on the forearm and
hand. Use the elbow joint as the axis of rotation.
b. If the net torque obtained in part (a) is nonzero, in
which direction will the forearm and hand rotate?
8. When a ceiling fan rotating with an angular speed of 2.55 rad/s is turned off, a frictional torque of
0.220 N·m slows it to a stop in 5.75 s. What is the moment of inertia of the fan?
14. A fish takes the bait and pulls on the line with a force of 2.1 N. The fishing reel, which rotates
without friction, is a cylinder of radius 0.055 m and mass 0.84 kg.
a. What is the angular acceleration of the fishing reel?
b. How much line does the fish pull from the reel in 0.25 s?
20. To determine the location of his center of mass, a physics student lies on a lightweight plank
supported by two scales 2.50 m apart. If the left scale reads 290 N, and the right scale reads 122 N,
a. The student’s mass.
b. The distance from the student’s head to his center of mass.
22. A school yard teeter-totter with a total length of 5.2 m and a mass of 36 kg is pivoted at its center.
An 18-kg child sits on one end of the teeter-totter.
a. Where should a parent push vertically downward with a force of 210 N in order to hold the
teeter-totter level?
b. Where should the parent push with a force of 310 N?
52. A torque of 0.12 N·m is applied to an egg beater.
a. If the egg beater starts at rest, what is its angular momentum after 0.50 s?
b. If the moment of inertia of the egg beater is 2.5 x 10-3 kg·m2, what is its angular speed after
0.50 s?
79. When you arrive at Duke’s Dude Ranch, you are
greeted by the large wooden sign. The left end of the
sign is held in place by a bolt, the right end is tied to a
rope that makes an angle of 20.0° with the horizontal.
If the sign is uniform, 3.20 m long, and has a mass of
16.0 kg, what is
a. The tension in the rope?
b. The horizontal and vertical components of the
force, F, exerted by the bolt?