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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.
Work is to energy as _____ is to angular momentum?
a. Angle
b. Angular impulse
c. Angular acceleration
d. Momentum
Applications
3. Two air hockey pucks are traveling toward each other at a relative speed of 4 m/s. Puck A has
a mass of 0.5 kg and puck B has a mass of 0.4 kg. They collide with central impact and a
coefficient of restitution of 0.8. If puck B is moving to the right with a speed of 3.5 m/s, how
fast is puck A moving?
4. How many revolutions does a CD initially spinning at 6000 rpm go through if it is subjected to
a constant deceleration and stops in 4 seconds?
5. What is the center of mass of the following two particle system:
m1=3 kg, r1=<-2, 0, 0> m, v1=<1, 0, 0> m/s
m2=5 kg, r2=<-1, 1, 0> m, v2=<0,-2, 0> m/s
6. What is the velocity of the center of mass of the two-particle system above?
R. Gist Spring 2007
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Ver. A
PES 111 General Physics I
Practice Exam 3
7. A car collides with a crash barrier and comes to a stop from its initial speed of 20 m/s in a time
of 0.1 s. What average force is exerted by the barrier on the car?
8. (4 pts) Find the cross product of A = <-1, 0, -1> and B = <3, 5, 0>.
9. A certain wheel is rotationally accelerated by firing two rockets on opposite edges of the wheel
tangent to the wheel’s rim. The wheel has a radius 0.5 meters and a moment of inertia of 0.16
kg*m2. If the acceleration rate is 10 rad/s2, what is the magnitude of the tangent force due to
the two rockets?
10. An angular momentum vector is changing with time and can be expressed as L = <3t, 2,
t2> kg*m2/s. What torque vector is being applied in order to accomplish this change?
11. What is the total kinetic energy of a sphere rolling without slipping at 10 m/s? Its mass is 20
kg and its radius is 10 cm. How far up an incline of 10o will it travel before stopping?
12. A 20 kg cylinder of length 0.5 m and 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 velocity vector due to
rotation? If the cylinder is initially located at <0, 3, 4> m and is moving parallel to the x-axis
at 5 m/s, what it its angular momentum vector due to this motion? What is its total angular
momentum vector?
13. Two uniform disks separated by a small distance are spinning about a common axis of rotation
at different speeds. Disk A, with mass 10 kg and radius 0.5 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?
R. Gist
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PES 111 Practice Exam 3