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Physics 1AL
ROTATIONAL MOTION
Summer Session II 2010
1
Introduction
The purpose of this lab is to study the various aspects of rotation.
You will be studying the
property of rotational inertia for various shapes and sizes.
Your Objective:
To determine how shape, size, mass, or distribution of mass affect the motion
of objects rolling down an inclined plane.
______________________________________________________________________________
Prelab questions:
Read
sections 7.1, 7.2, 7.3, 7.4, 8.5, and 8.6 in Serway & Faughn
Answer
each of the following questions in a few sentences of your own words:
1.
Suppose you have two equal mass objects both on a gentle incline.
One is a glider on an
air track while the other is a ball on a straight slope.
The air track and the slope have the
same slope angle.
You release them at the same time and at the same distance from the
bottom of the slope.
You note that neither loses any significant amount of energy to
friction as the air track has very low friction and the ball rolls down without slipping or
sliding.
a) Explain what type of energy both objects have just before they are released.
Do both
objects initially have the same amount of energy?
b) Explain what type of energy both objects have just before they reach the bottom of
the slope.
Do both objects have the same amount of energy when they reach the
bottom of the slope?
2.
Calculate the moment of inertia about a central axis (in units of kg m
2
) for:
a)
a solid sphere with a mass of 75 grams and a radius of 5.0 cm.
b)
a thin spherical shell with a mass of 75 grams and a radius of 5.0 cm.
c)
a solid cylinder with a mass of 75 grams and a radius of 5.0 cm.
d)
a thin hoop with a mass of 75 grams and a radius of 5.0 cm.
3.
Calculate the rotational kinetic energy for the following objects spinning about a central
axis (in units of Joules):
(Hint:
the answers to question 2 may help here)
a) a solid sphere with a mass of 75 grams and a radius of 5.0 cm rotating with an
angular speed of 1.5 rad/sec.
b) a thin spherical shell with a mass of 75 grams and a radius of 5.0 cm rotating with an
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This note was uploaded on 09/25/2010 for the course PHYSICS 1A 1al taught by Professor Rafaelski during the Summer '10 term at UCSD.
 Summer '10
 Rafaelski

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