Momentum

What is momentum? ~ Newton’s Quality of MotionUse the 2nd Law…F = ma to describe how

momentum can change when a force acts on it.F=ma m ∆v

∆t Multiply both sides by ∆t :

F ∆t = m ∆vImpulse Momentum

Linear Momentum

Linear momentum- the product of mass and velocity of an object.

Symbol : p p = mv

Units: kg m/s or N s

Impulse – the product of the average force and the time interval over which it acts.

Symbol: J J = F ∆t

Units: N s or kg m/s

Impulse-Momentum Theorem

F ∆t = ∆p (change in momentum)

F ∆t = p2 - p1

The impulse of an object is equal to the change in momentum it causes.

What causes a change in velocity?- an unbalanced force

Examples: airbags, egg falling on the floor vs. on a bed

Impulse- Momentum

A force applied causes a change in momentum:F ∆t = ∆p

F ∆t = p2 - p1

So … p2 = F ∆t + p1

m2v2 = F ∆t + m1v1

and

F ∆t = m2v2 – m1v1

Conservation Of Momentum

Closed system – any system that does not gain or lose mass.

***all forces within the system are internal***all forces outside the system are external Isolated system – the net external force on a

closed, isolated system is zero.Law of Conservation of Momentum – the

momentum of any closed, isolated system with no net external force, does not change.

pinitial = pfinal

Conservation Of Momentum

m1∆v = m2∆v

When dealing with collisions with before and after scenarios, write an equation for EACH object for the BEFORE and AFTER.

m1 v1 + m2 (at rest) m1v1 + m2v2