Do NOT plug in numbers until you have solved for the desired variable!
Try to solve each problem algebraically first.
Leader: Wesley
Worksheet #19 Torque and
Course: PHYS 221
Energy in Rotational Motion
Instructor: Whisnant
Supplemental Instruction
Date: 03/10/2014
Iowa State University
1. (Torque and Angular Acceleration) A book of mass m sits on a frictionless horizontal
table. The book is attached to a mass string that passes over a pulley of diameter d. The
other end of the string is attached to a second hanging book of mass M. The system is
released from rest and is observed to move a distance h in time t.
a. What is the tension in each part of the cord?
b. What is the moment of inertia of the pulley about its rotational axis (CM)?
m = 2.00 kg
d = .150 m
M = 3.00 kg
h = 1.20 m
t = .800 s
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Do NOT plug in numbers until you have solved for the desired variable!
Try to solve each problem algebraically first.
2. (Rotational Kinetic Energy) Two metal disks, one with radius R1 and mass M1, and the
other with radius R2 and mass M2.
a. What is the total moment of inertia of the two disks?
b. A mass of m is hung via a string wrapped around the lighter disk, and hangs a
distance h above the floor. If the mass is released from rest, what is its speed just
before it hits the floor?
c. Repeat part (b) if it the mass is hung from the heavier disk.
M1 = .80 kg
R1 = 2.50 cm
M2 = 1.60 kg
R2 = 5.00 cm
m = 1.50 kg
h = 2.00 m
Do NOT plug in numbers until you have solved for the desired variable!
Try to solve each problem algebraically first.
3. (Rolling without slipping) A bowling ball rolls uphill at an angle θ to the horizontal.
The bowling ball can be treated as a uniform solid sphere.
a. Draw the free body diagram of the bowling ball. Which direction should the force
of friction be pointing?
b. What is the translational acceleration (acceleration of the center of the ball) of the
ball?
c. What minimum coefficient of static friction is needed to keep the ball from
slipping?