Vocabulary Quiz-Friday

How difficult is it to get something to change its momentum?

P=mv

What could be manipulated in order to change the football player’s momentum?

• Brick wall?

• Dinosaur eating football player?

P=mv

A change in momentum would mean a change in either the mass or velocity.

We’ll always assume the velocity changes.

What causes a change in velocity?

a Force

Impulsealso known as change in momentum

Impulse= (force)(time)

= FΔt

Unit is Newton-second

N-s

Increasing Momentum

Increasing Momentum“Follow through” in sports

1) Apply the greatest force possible for the longest time possible

Impulse= (force)(time)

= FΔt

Decreasing Momentum

• http://www.hailstate.com//mediaPortal/player.dbml?DB_OEM_ID=16800&id=661846&db_oem_id=16800

Decreasing Momentum

The change in momentum may be b/c of a small force exerted over a long time

The change in momentum may be b/c of a large force exerted for a short time

Decreasing Momentum

To minimize the effect of the force on an object involved in a collision, the time must be increased.

Other examples that decrease the force by increasing the time

• Air bags• Catching a baseball

with a glove• Fighting with padded

gloves v. bare fists• Rolling with a punch

Padded dashboards• Packing materials• Crumple zones• New seat belts

Practical application

Observe that the greater the time over which the collision occurs, the smaller the force acting upon the object.

Cradling the ballA water balloon is thrown high

into the air and successfully caught. The key to the success is to contact the balloon with outstretched arms and carry the balloon for a meter or more before finally stopping its momentum. The effect of this strategy is to extend the time over which the collision occurred and so reduce the force.

This same strategy is used by lacrosse players when catching the ball. The ball is "cradled" when caught;

Other examples where extending your time decreases the force

• Bungee jumping

• Bending your knees when you jump, not locking them

• Safety nets/ giant air mattresses (during fires, circuses)

Impulse Activity

• Monday it is supposed to be 80 degrees

• Good Luck!