Impulse of a force - effect on linear and angular momentum

1. Apr 23, 2012

Froskoy

Hi,

I'm having trouble understanding what the relation is between the impulse of a force during a collision and the changes in linear and angular momentum during the collision.

I know that the principle of conservation of linear momentum says that the total linear momentum before is equal to the total linear momentum after and the principle of conservation of angular momentum states that the total angular momentum before is equal to the total angular momentum after, but am struggling with the interpretation of this.

Do these principles mean that

1) the sum of the impulse + linear momentum before + angular momentum before = linear momentum before + angular momentum after

OR

2) (the sum of impulse + linear momentum before = linear momentum after) AND ALSO (the sum of impulse + angular momentum before = angular momentum after)?

With very many thanks,

Froskoy.

2. Apr 23, 2012

tiny-tim

Hi Froskoy!

Linear momentum and angular momentum can't be added.

(for a start, linear momentum is a vector, but angular momentum is a pseudovector!)

it's 3) … (the sum of impulse + linear momentum before = linear momentum after) AND ALSO (the sum of torque (or moment) of impulse + angular momentum before = angular momentum after)

3. Apr 24, 2012

morrobay

There is no substitute for a good Physics text. Following from Halliday - Resnick
p2 - p1 = integral 1>2 dp = integral 1>2 Force dt = Impulse

The integral of force over the time interval during which force acts is called the
impulse of the force and is equal to the change in momentum. Both the impulse
and linear momentum are vectors and have same units and dimensions.
And is area under force time curve.
integral t1>t2 Force dt

4. Apr 29, 2012

Froskoy

Thanks very much! It all makes a lot more sense now!

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook