Impulse

Chapter 8.2

An impulse transfers momentum

http://www.youtube.com/watch?v=YFzNKBZehSU

Impulse Objectives (leave space between each question)

1. What is impulse?2. What is the impulse equation?3. What occurs through impulse?4. How are impulse and change in

momentum related?5. How does the time of momentum

transfer affect the force of impact?

Impulse1.What is impulse?

Impulse is the product of force (F) times time (t)

an impulse transfers momentum2.What is the impulse equation?

The impulse equation is I = Ft I is the symbol for impulse F is the impact force t is the momentum transfer time Unit for impulse is N x s (same as kg x m/s)

3.What occurs through impulse?Momentum transfer occurs through impulse

Impulse4.How are impulse and change in momentum

related?

Impulse is equal to a change in momentum

Ft = ∆mv

5.How does the time of momentum transfer affect the force of impact?

The time it takes for momentum to be transferred (or change) determines how much force per unit time will be experienced.

impulse = change in momentum

Ft = ∆mv

8.2 Impulse Changes Momentum

•The impulse you give will be the impulse you get back: The force of the impulse will vary inversely with time.

Impulse

The impulse and the change in momentum are the same in each case.

Impulse

By increasing the time needed to change the momentum of an object, the amount of force applied per unit time is reduced.

Impulse

By decreasing the time needed to change the momentum of an object, the amount of force applied per unit time is increased.

If the change in momentum occurs over a long time, the force of impact is .

8.2 Impulse Changes Momentum

small.

If the change in momentum occurs over a short time, the force of impact is

8.2 Impulse Changes Momentum

large.

Because the bowling ball is moving, it has _______________, which is the product of ______ x __________.

When the bowling ball collides with a barrier, it transfers ___________ to the barrier through _________, which is the product of ________ x __________.

Remember…

Extend the time of momentum transfer, reduce the force of impact.

Impulse with large time has small force compared to same impulse with short time, which would have a large force. RM

Momentum is mass in motion (p = mv) An impulse transfers momentum (I = Ft). Impulse remains the same, but time of transfer

and impact force will vary inversely.

Impulse = change in momentumFt = ∆mv

More time, less force Less time, more force

Same momentum, same impulse

Momentum and impulse

Impulse and Safety

Safety in collisions can be achieved by extending the momentum transfer time in which the impact force acts.

SLOW TRANSFER OF MOMENTUM Transferring momentum over a longer

period of time requires a smaller force. Consider how materials

GIVE

The safety net reduces the stopping force on a fallen acrobat by substantially increasing the time interval of the contact

DEVICES THAT INCREASE MOMENTUM TRANSFER TIME Traffic Crash Cushions

When you extend the time of transfer, you reduce the force.

DEVICES THAT INCREASE MOMENTUM TRANSFER TIME Air Bags

When you extend the time of transfer, you reduce the force.

DEVICES THAT INCREASE MOMENTUM TRANSFER TIME Bungee Cords

When you extend the time of transfer, you reduce the force.

QUICK TRANSFER OF MOMENTUM Transferring momentum in a short period

of time greatly increases the impact force!

When you reduce the time of transfer, you increase the force.

The impulse provided by a boxer’s jaw counteracts the momentum of the punch.

a. The boxer moves away from the punch.

8.2 Impulse Changes Momentum

The impulse provided by a boxer’s jaw counteracts the momentum of the punch.

a. The boxer moves away from the punch.

b. The boxer moves toward the punch. Ouch!

8.2 Impulse Changes Momentum