PHYSICS 1403, QUIZ 3
Chapter 6, July 25, 2006
Partial credit will be LIBERAL, provided that you show your work! USE BACK IF NEEDED!
(Please tell me if you’ve done so!)
Name: ______________________
1. (10 points) CONCEPTUAL QUESTIONS!! Using complete, grammatically correct,
English sentences, answer the following questions:
a. State the Work-Energy Principle. (You may supplement the sentences with equations if you
explain what each symbol means.)
b. State the Principle of Conservation of Mechanical Energy. (You may supplement the
sentences with equations if you explain what each symbol means. Note: This ISN’T the same as
the Law of Conservation of Total Energy, which states that energy can neither be created nor
destroyed but can only be transformed from one form to another!).
2. (20 points) Note: This problem can be solved either using the Newton’s 2nd Law (Force)
methods of Ch. 4 or the Energy Methods of Ch. 6. This is a quiz over Ch. 6, so you MUST
USE ENERGY METHODS TO SOLVE THIS PROBLEM! You’ll get no credit for using
the Force methods of Ch. 4! You don’t need to resolve forces into components to solve this
problem!! See figure. A mass m = 250 kg, initially at rest, slides down a frictionless
inclined plane. The initial height is y = 4.5 m above the floor. The incline angle is 37°.
y = 4.5 m, v = 0 
y = 0, v = ?


Before
After
a. Compute (find a numerical value for) the gravitational potential energy of the mass at its
initial position (left figure). How much work must be done by gravity to move the mass
down the incline?
b. Compute (find a numerical value for) the kinetic energy of the mass at the bottom of the
incline (right figure). Find it’s speed there.
c. Compute (find numerical values for) the kinetic energy and the speed of the mass
when it is 2.5 m above the floor (not shown in the figure)