M o m e n t u m

Momentum is…

•Inertia in motion

•Mass x Velocity

Creating Momentum

•Greater Force = Greater Momentum

Force creates acceleration, so pushing harder makes you go faster.

Impulse is…• Force applied x Time applied• Change in Momentum

Therefore…•Δ(mv) = Ft

Impulse is…• Commonly confused with

impact (be careful)

• The force applied

• Determined by solving the equation for forceFt m v

MomentumIncreasing Momentum:–Increase force or time

–Greatest momentum:• Big force for big time

MomentumDecreasing Momentum

–When you stop you lose all of your momentum – impulse is same no matter how you stop

–More time means less force (haystack)–Less time means more force (brick

wall)

A Picture is Worth a Thousand Words

Man moves back, increasing time and

decreasing force

Man leans in, decreasing time and

increasing force

Bouncing• When something bounces the impulse

is greater because you bring velocity to 0 and then increase it the other way

A few more examples• Conservation of momentum can also be shown

with moving objects that undergo a weight change.– The following examples show a freight train that has

weight added to it while it is moving – notice the change in velocity that occur with the weight increase

• Are mass and velocity proportional or inversely proportional?

Big Cart, Little Brick

Little Cart, Big Brick

The Fish Example Part #1

The Fish Example Part #2

Conservation in Collisions

• Net Momentum Before = Net Momentum After –Friction is usually considered to be

negligible during the collision itself

Collision Types–Elastic collisions objects are not

deformed or attached and don’t generate heat or sound.

–Inelastic collisions colliding objects become tangled or coupled together. They still follow the law of conservation, but after the collision they are attached to each other.

Inelastic Collision Example #1

This demonstration illustrates an astronaut in a frictionless environment undergoing an inelastic collision with another astronaut

Inelastic Collision Example #2

Inelastic Collision Example #3

Inelastic Collision Example #4

Inelastic Collision Example #5

Elastic Collision Example #1

Elastic Collision Example #2

Elastic Collision Example #3

Look at the difference…

Look at the difference…

Look at the difference…

Momentum Vectors Momentum vectors combine like all other

vectors. When looking at the vectors involved in a

collision the vector(s) before and after the collision must have the same resultant.

Vector Collision Example