PHYS115 Concepts of Physics Quiz 5 Chapter 6
Hewitt, 8th ed.
Name __________________
15 Points
Score _______
September 29, 2000
Box # __________
1 hp = 746 W
1. ____
Which of the following is not a correct statement about work?
A.
B.
C.
D.
2. ____
Work is a scalar quantity.
When an object is moving in a direction opposite to the direction of a force acting on it that force does
negative work and decreased the energy of the object.
Work is done on an object by a force only when the force has a component that is in the direction of the
motion or opposite to that direction.
When an object moves on a level surface the force of gravity does work on the object that is equal to the
weight of the object times the distance that it moves.
What is the kinetic energy of a car that has a mass of 800 kg and moves with a speed of 30 m/s?
A.
B.
3. ____
720,000 J
24,000 J
C.
D.
360,000 J
48,000 J
What is the increase in the potential energy of a Concepts of
Physics student when she walks up an inclined plane that is 20
m long with the high end 6 m above the low end? Her mass
is 60 kg.
A.
B.
4. ____
1,200 J
3,528 J
C.
D.
360 J
11,760 J
A motorist is driving her car on a highway when she sees a traffic light a head change to red. She applies
her brakes. How much work is done on a car by a braking force of 5000 N while the car moves a distance
of 40 m? The car has a mass of 900 kg.
A.
B.
5. ____
-200,000 J
36,000 J
C.
D.
20,410 J
-132,800 J
How much time is required for a .5 hp motor to deliver 15,000 J of work?
A.
B.
40 s
20 s
Turn the page for question 6
C.
D.
80 s
300 s
6.(10) A constant upward force of 300 N is applied to an object that has a mass of 20 kg. Only this force and gravity act
on the object. The object is initially at rest and is raised upward a distance of 4 m. Answer each of the following
questions for this situation.
Part A (3) How much work is done on the object by the upward force?
W = F d = 300 N @ 4 m = 1200 J
Part B (3) What is the increase in the potential energy of the object?
)PE = m g h = 20 kg @ 9.8 m/s2 @ 4 m = 784 J
Part C (4) What is the final kinetic energy of the object? What principle did you apply to answer this question?
KEfinal + )PE = W = 1200 J
Answers:
1. D
2. C
3. D
so KEfinal = 1200 J - 784 J = 416 J
4. A
5. A