Chapter 11 Class 11

Published on November 2016 | Categories: Documents | Downloads: 69 | Comments: 0 | Views: 999
of 3
Download PDF   Embed   Report

Comments

Content

Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.

Chapter 11: Angular Momentum





Vector Products
Torque
Angular Momentum
Conservation of Angular Momentum

Vector (Cross) Product
Remember the definition of torque:

  rF sin 

We now define a new vector
relationship:

Vector or Cross Product

C  AB

C  AB sin 

Torque

Angular Momentum
Example: 1 kg particle moving to
the right at constant speed 5 m/s,.
Find the angular momentum at the
instant it’s position was 5i+10j

τ  rF

τ  rF

F

dp
dt

dr
 v // p
dt

We can add a quantity equal to zero

  rF sin 

dp

dr

 τ  r  dt  p  dt 

 dL
 τ  dt

where

p

dr
0
dt

d r  p 
dt

angular momentum
SI unit kg.m /s
  
L  r p
2

Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.

Angular Momentum of a Rotating
Rigid Object

Example: Bowling ball
  10rev / s

For an object rotating
about the z-axis:

L?

Lz  I
The angular momentum
and velocity are along the
z-axis

Conservation of Angular
Momentum


The total angular momentum of a system is
conserved if the net external torque acting on the
system is zero.

L  constant



The initial and final angular momentum of an
isolated system is constant after an internal
rearrangement.
L i  L f  constant



For a rigid rotating object:
I i i  I f  f  constant

Example

Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.

Example

Example

Review
Vector Product

C  AB

Torque

τ  rF

Angular Momentum

L  r p

τ 


C  AB sin 

Lz  I

dL
dt

Angular momentum is conserved

Sponsor Documents

Or use your account on DocShare.tips

Hide

Forgot your password?

Or register your new account on DocShare.tips

Hide

Lost your password? Please enter your email address. You will receive a link to create a new password.

Back to log-in

Close