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
Applications
2. Two air hockey pucks are traveling toward each other. Puck A has a mass of 0.6 kg and is
moving at 2 m/s to the right. Puck B has a mass of 0.4 kg and is moving 2 m/s to the left.
They collide with central impact. Their coefficient of restitution of 0.8. How fast is puck A
moving after the collision?
3. 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?
4. A 2000 kg 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?
5. 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?
R. Gist
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Long Semester Ver. A, Rev. 1
PES 111 General Physics I
Practice Exam 3
6. 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?
7. Find the cross product of A = <-1, 0, -1> and B = <3, 5, 0>.
8. 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?
9. 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?
10. 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?
R. Gist
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Long Semester Ver. A, Rev. 1