PES 111 General Physics I
Practice Exam 3
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You may use one regular (3” x 5”) index card for your formulas or any other notes or
diagrams you think you may need (front & back).
Definitions & Concepts
1. Which pairs of vectors always point in
the same direction?
a. Torque and force
b. Position and velocity
c. Angular velocity and angular
momentum
d. Position and angular momentum
2. The state of an object or system in
which all external forces are in balance.
a. Stress
b. Dynamics
c. Equilibrium
d. Strain
3. What is the magnitude of the phase
angle difference between the position
and the velocity of an object
undergoing simple harmonic motion?
a. 0o
b. 90o (π/2)
c. 180o (π)
4. A simple harmonic oscillator
experiences drag forces due to air, and,
after several bounces, comes to rest.
What type of oscillatory motion is this?
a. Driven oscillation
b. Over-damped oscillation
c. Under-damped oscillation
d. Resonance
Applications
5. Find the cross product of A = <-1, 0, -1> and B = <3, 5, 0>.
6. The angular momentum of an object is changing with time and can be expressed as the vector
L = <3t, 2, t2> kg*m2/s. What torque vector is being applied in order to accomplish this
change?
7. How much closer (in km) is Mars to the sun when at perihelion than at aphelion?
8. A 20 kg cylinder of length 0.5 m and radius 0.25 m is spinning about its long axis (which is
directed along the positive z-axis) with a speed of 5 rad/s. What is its angular momentum
vector due to rotation? If the cylinder is initially located at <0.0, 0.3, 0.4> m and is
moving parallel to the positive x-axis at 5 m/s, what it its angular momentum vector due to this
motion with respect to the origin? What is its total angular momentum vector?
R. Gist
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Ver. A, Rev. 3
PES 111 General Physics I
Practice Exam 3
9. Two uniform disks separated by a small distance are spinning about a common axis of rotation
at different speeds. Disk A, with mass 12 kg and radius 0.6 m, is spinning at 15 rad/sec. Disk
B, with mass 10 kg and radius 0.5 m, is spinning in the opposite direction at 15 rad/sec. Disk
B is dropped onto disk A and the two disks interact until they reach a final common angular
speed. What is this speed?
10. What is the escape velocity from the surface of the planet Mars, whose mass is 6.46x1023 kg
and whose radius is 2.109x106 m? What is the surface gravitational acceleration on Mars?
11. A lead sphere is formed with a diameter of 1 m and a mass of 5760 kg. What is the magnitude
of the gravity field due to this sphere at a point 2 meters from its surface? If a small lead
sphere of diameter 0.01 m and mass 0.00576 kg is placed 2 meters from the surface of the large
sphere, what is the magnitude of the gravitational force of the large sphere on the small one?
12. What is the tension in cable AC in the diagram to the right?
13. A length of wire of unknown metal with diameter 0.4 mm and originally 2.000 meters long is
observed to stretch to 0.01 mm when a weight of 100 N is hung from its end. What is the value
of Young’s modulus of the unknown metal?
R. Gist
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Ver. A, Rev. 3
PES 111 General Physics I
Practice Exam 3
14. A 3 meter uniform beam (AD)
weighing 300 N is supported by a
strut at B and a cord at D. A box
weighing 20 N is placed at C. If
distance AB is 0.6 meters and
distance BC is 1.6 meters, what is
the tension in the cord? What is the
compression in the strut?
15. A simple harmonic oscillator is built from a 10 kg block on wheels attached to a wall using a
horizontal spring (with spring constant k=9000 N/m). At time t=0, the block is struck to start it
oscillating, such that its initial speed as it leaves equilibrium (x=0) is 10 m/s. Find the
following: (a) The angular frequency of the oscillation; (b) The period of oscillation of the
block; (c) The maximum displacement of the block; (d) The maximum acceleration of the
block; (e) The total energy contained in the system; (f) The distance from equilibrium of the
block at t=0.5 seconds.
16. A 4 kg thin ring of diameter 1 meter hangs from a nail in a wall. If the ring is
started rocking about the nail with a small angular displacement, what is the
period of oscillation of the ring?
Constants:
Universal Gravitational Constant
Radius of Mars
Mass of Mars
Mars
Mean distance between Mars and the sun
Eccentricity of Mars orbit
Mean distance between Earth and the sun
R. Gist
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G=6.67 x 10-11 N*m2/kg2
RMars=2.109x106 m
MMars=6.46x1023 kg
d=1.52 AU
e=0.093
dS=1.497 x 1011 m (1 AU)
Ver. A, Rev. 3