Transcript Lecture18

READING QUIZ
Torque primarily depends on:
• angular acceleration.
• angular velocity.
• angular mass.
Rotational Inertia
The resistance to change in rotational motion.
  I
Torque = Moment of inertia x angular acceleration
I  mr
2
Moment of Inertia = Mass x distance from axis squared
Figure 8.15
Expressions for the rotational inertia of
several objects, each with a uniform distribution
of mass over its volume. The letter m is used to
represent the total mass of the object.
Physics of Angular Motion
If the total torque on an object is zero, then it
does not rotate, or it rotates at a constant
angular velocity.
Physics of Linear Motion
If the total force on an object is zero, then
it does not move, or it is in linear motion
with constant velocity
CONCEPT
Linear Motion
Rotational
Inertia
m
I
Second Law
F=ma

Momentum
P=mv
L=I
conservation
P=constant,
if F=0.
KE=1/2mv2
L=constant,
if 
KE=1/22
Kinetic energy
Fig. 8.16
Physics of Angular Motion
If the net torque on a system is zero, the total
angular momentum of the system is
conserved.
L=I
L = vector
I = Tensor
 = vector
Fig. 8.17
Fig. 8.18
Fig. 8.20
Rotational velocity is a vector. Use the right hand rule
to find the direction…..
Fig. 8.24