Define momentum Define impulse Relate impulse and momentum to everyday

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# Define momentum Define impulse Relate impulse and momentum to everyday - PowerPoint PPT Presentation

Define momentum Define impulse Relate impulse and momentum to everyday. In life - momentum describes something “on a roll” that is difficult to stop. In physics - momentum describes a quantity of motion . If an object is in motion then it has momentum. "mass in motion".

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## Define momentum Define impulse Relate impulse and momentum to everyday

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Presentation Transcript

Define momentum

• Define impulse
• Relate impulse and momentum to everyday

In life - momentumdescribes something “on a roll” that is difficult to stop.

In physics - momentumdescribes a quantity of motion.

If an object is in motion then it has momentum.

"mass in motion"

Inertia

Velocity

p = mv

Momentum is a vector quantity. It has the same direction as the objects velocity.

Every moving object has momentum.

To bring the object to rest we must apply a force to change this momentum to zero.

Estimate the mass of each object and estimate its velocity to try to order the following objects in increasing momentum:

statue

Bus

football

sprinter

skateboarder

race car

slapshot

PHYSICS

A textbook at rest has no momentum. To make the book move you must overcome friction and the book’s inertiaby applying a force.

A force accelerates the book, giving it a velocity. The book now has forward momentum, and the inertia of the book continues the motion forward.

Impulse

Momentum

To change an objects motion (momentum) we need to applyan unbalanced force.

Increased momentum

Unbalanced Force

Decreased momentum

Unbalanced Force

The amount of unbalanced force and the time during which the force is applied is the impulse.

I = F·t

Impulse equals force multipled by time

t

F

A force for a given amount of time will result in a mass undergoing a change in velocity.

m·∆v

=

=

I

F·t

Impulse equals a change in momentum

t

F

0 m/s

10 m/s

2 seconds

F·t

20 kg

0 m/s

10 m/s

m·∆v

=

100 N

=

100·2

200

20·10

200

4 seconds

F·t

20 kg

10 m/s

0 m/s

=

m·∆v

50 N

20·(-10)

-200

=

4

(-50)·

-200

TWO ways to apply a large impulse to an object and make a BIG change in momentum –

• apply a LARGE forcefor a small time,

Impulse = (Force) (time)

• apply a small force for LONG time.

Impulse = (Force) (time)

Inertia keeps the passenger moving forward with the same momentum as before (speed of the car).

Impulse = (Force) (time)

Stopping a passenger requires an impulse.

If the time can be made longer then the stopping force will be made smaller.

Small forces will cause fewer injuries to passenger.

In every sport where you hit something you are told to “follow through.”

Following through increases the TIMEthat your force acts on the object, which makes for a larger change in velocity (momentum)

F

m

∆v

·t

=

m

m

500

=

(.2)

+ 200 m/s

0.5

500

(.1)

=

+ 100 m/s

No follow

0.5