• The candidate’s campaign lost a lot of MOMENTUM when his political partner was impeached

• After those 5-in-a-row winning blackjack hands, Lefty Loosie really had MOMENTUM

• Although the receiver snapped a hamstring at the 3 yard line, his MOMENTUM carried him into the endzone for a touchdown

• Today the stock markets gained MOMENTUM when Microsoft and IBM forecasted large earnings

Momentum

• Momentum -• Product of mass and

velocity • Symbol: p• Formula: p = mv• Units: kg.m/s

Law of Conservation of Momentum

• p lost = p gained• “total p in a system

remains the same if no external forces act on the system”

• momentum is therefore conserved

pbefore = pafter

Energy and Momentum

• the higher the roller coaster the more the PE, so the greater the KE that is possible

PEtotal = KEtotal

• Impulse -• The product of Force

and time• Symbol: I• Formula: I = F.t• Units: N.s• N.s = kg.m/s• A longer t results in a

smaller F

Applications of Momentum & Impulse

• The longer you contact a ball when you’re catching it, the less the impact hurts

• Impulse = Ft• The greater the mass

of parts that fly off in a collision the safer the occupants

Airbags work because they increase your contact time with a surface

More Everyday Applications

• You give a hammer momentum by swinging it harder

• Hammers have to be relatively heavy to get the job done (ie: can get more momentum!)

In a car wreck, each car part that flies off carries with it momentum. Each piece has mass and velocity and the total momentum before the collision must equal the total momentum after the collision.

pbefore = pafter

Elastic Inelastic

(billiards, Newton’s (skateboarder jumps on

Cradle) skateboard)

-objects bounce off -objects stick together

after collision after collision

-no E lost to heat or sound -involves a loss of KE

-does not cause damage -causes damage

FORMULA: FORMULA:

(mava +mbvb)1 = (mava +mbvb)2 [mava + mbvb]1= [(ma+mb)vab]2

Problem A - A baseball with a mass of 0.14 kg moves at 35 m/s. a) find “p” b) Find the v at which the baseball and a bowling ball with a mass of 7.26 kg would have the same “p”

a) m = 0.14 kg

v = 35 m/s

b) m = 7.26

v = ?

p = mv

p = (0.14)(35) = 4.9 kg m/s

p = mv

4.9 = 7.26 v = 0.67 m/s

Problem B - Glider A with a mass of 0.355 kg and a v of 0.095 m/s collides with Glider B of mass 0.710 kg moving in the same direction at 0.045 m/s. After colliding, Glider A continues in the same direction with a v of 0.035 m/s. What is Glider B’s v? (is this ELASTIC or INELASTIC?)

ma1= 0.355 kg

va1 = 0.095 m/s

mb1 = 0.710 kg

vb1 = 0.045 m/s

va2 = 0.035 m/s

It is ELASTIC, so use…

(mava +mbvb)1 = (mava +mbvb)2

(.355)(.095) +(.710)(.045) = (.355)(.035) +(.710)(vb2) =

Problem C - A skateboard with mass 0.75 kg and a v of 1.0 m/s is jumped on by a person of mass 63.00 kg running at 2.0 m/s. What is the v of the person on the skateboard after the “collision”? (Is this ELASTIC or INELASTIC?)

ma = 0.75 kg

va = 1.0 m/s

mb = 63.00 kg

vb = 2.0 m/s

vab = ?

It is INELASTIC, so use…

[mava + mbvb]1 = [(ma+mb)vab]2

(.75)(1.0) +(63.00)(2.0) = (.75+63.00)(vab) =

Summary -

Name Symbol Units Formula

momentum p kg.m/s p = mv

impulse I kg.m/s Ft

Other Formulas -

elastic collision (mava +mbvb)1 = (mava +mbvb)2

inelastic collision [mava + mbvb]1 = [(ma+mb)vab]2