Worksheet #36 – Thermal
Processes, Heat Capacities
Supplemental Instruction
Iowa State University
Leader:
Course:
Instructor:
Date:
Wesley
PHYS 221
Whisnant
04/28/2014
Review Questions
1. (76.8%) You are trying to move a dresser of height of H = 1.6 m, mass m = 35 kg, and
width L = 0.70 m. If the coefficient of kinetic friction is 0.20, what is the maximum
height h, in m, that you can apply a force so that it moves at constant velocity and does
not tip over?
2. (79.9%) A block of mass 3.5 kg is attached to a very light string, which is wrapped
around a uniform, solid cylinder of radius 0.40 m and mass 2.0 kg. The cylinder is
suspended from the ceiling by a fixed cable. When the block is released and allowed to
fall, what is the tension in the string, in N?
1060 Hixson-Lied Student Success Center  515-294-6624  sistaff@iastate.edu  http://www.si.iastate.edu
Do NOT plug in numbers until you have solved for the desired variable!
Try to solve each problem algebraically first.
3. (62.0%) A rod of length 2.4 m and mass 7.5 kg is hinged at one end so that the rod can
rotate without friction as shown. If the rod is released from rest in the horizontal position,
what is its angular velocity, in rad/s, when it reaches the vertical position?
Today’s Topics
1. (Thermal Processes) The temperature of of .150 moles of an ideal gas is held constant at
77.0 degrees C while its volume is reduced to 25% of its initial volume. The initial
pressure of the gas is 1.25 atm.
a. Determine the work done by the gas.
b. What is the change in its internal energy?
c. Does the gas exchange heat with its surroundings? If so, how much? Does the gas
absorb or release heat?
Do NOT plug in numbers until you have solved for the desired variable!
Try to solve each problem algebraically first.
2. (Adiabatic Processes) Two moles of carbon monoxide (CO) start at a pressure of 1.2 atm
and a volume of 30 liters. The gas is then compressed adiabatically to 1/3 of this volume.
Assume that the gas may be treated as ideal. What is the change in internal energy of the
gas? How does the temperature relate to this change?