PES 111 General Physics I
Practice Exam 2
3Definitions & Concepts
1. (3 pts) Which SI unit measures energy?
A. The newton
B. The watt
C. The erg
D. The joule
2. (3 pts) Which has more kinetic energy: a 2.5-kg ball traveling upward at 2 m/s, or a 1-kg
ball traveling sideways at 4 m/s?
A. The 2.5-kg ball
B. The 1-kg ball
Applications
3. (5 pts) A pick-up truck exerts a constant horizontal force of 3000 N while dragging a 300 kg
log 20 meters from rest. Assume a coefficient of kinetic friction of 0.8 between the log and the
ground.
A. What work is done by the force of the truck?
B. What work is done by gravity?
C. What work is done by friction?
D. What is the speed of the log at the end of the 20 meters?
G
4. (4 pts) A force is exerted on a particle. How much of the force F = (10iˆ − 20 ˆj ) N is in the
direction of 3/5 iˆ - 4/5 ĵ ? If the particle moves 2 meters in that direction, what work is done
by the force?
5. (4 pts) How much power is required to lift a 1200 kg piano upward at a constant speed of 2
m/s? If a motor delivers this power with an efficiency of 0.3, how much power must be
supplied to the motor? How much work is done on the piano after lifting it 4 meters?
6. (5 pts) A roller coaster car begins with a speed of 10 m/s at the top of a 5 meter incline.
Assuming frictionless and drag-free motion down the incline, what is its speed at the bottom?
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PES 111 General Physics I
Practice Exam 2
7. How much potential energy is stored in a spring with a spring constant 100 N/m that is
compressed 0.2 meters from its unstretched length? How much more must the spring be
compressed to double this energy?
8. (4 pts) How much energy is gained or lost in forming a 3-He nucleus from two separate
protons and a neutron?
9. 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?
10. 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?
11. 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
12. What is the velocity of the center of mass of the two-particle system above?
13. 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?
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PES 111 General Physics I
Practice Exam 2
14. 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?
15. 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?
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