PHYSICS 1403, QUIZ 3
Chapter 6, July 25, 2005
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) See figure. Note: This problem can be solved using either the Ch. 4 Force
methods or the Ch. 6 Energy Methods. This is a quiz on Ch. 6, so you are MUST USE
ENERGY METHODS TO SOLVE THIS! You will get NO credit for using Ch. 4 methods! L
You don’t need to resolve forces into components to solve this!! A mass, m = 35 kg, hangs
vertically from a cord of length L. It is given an initial horizontal velocity v0 = 12 m/s as
shown. It then swings up to a height h above its initial position, where it stops and turns
around. The length L and the angle θ aren’t needed to solve this!
v0
a. Compute (find a numerical value) the kinetic energy of the mass at its initial

v1 = 0
h
position.
b. Compute (find a numerical value) the gravitational potential energy of the mass at the
height h. Compute the height h. What Physical Principle did you use to do this
calculation?
c. Compute the work (find a numerical value) that was done against gravity to move the mass
up to the height h.
d. Compute (find numerical values) the potential energy and the height y of the mass when
it’s speed has decreased to v2 = 8 m/s.
y=0