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# Momentum PowerPoint PPT Presentation

Momentum. Definition. Formula. Units. Momentum. Vector quantity Direction matches direction of velocity. Example #1. Impulse equals change in momentum…. Example #2.

Momentum

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Momentum

### Momentum

• Vector quantity

• Direction matches direction of velocity

### Example #2

A 1400 kg car moving westward with a velocity of 15 m/s collides with a utility pole and is brought to rest in 0.30 s. Find the magnitude of the force

exerted on the car during the collision.

### Example #3

A 2250 kg car traveling to the west slows down uniformly from 20.0 m/s to 5.00 m/s. How long does it take the car to decelerate if the force on the car is 8450 N to the east? How far does the car travel during the deceleration?

4.00s

### Practice 6C p213 #1-3

• Right now in class…

### Why are dashboards in automobiles padded?

• Longer time interval requires a smaller force to achieve same momentum change

• When egg hits the plate the time period is shorter & force is greater

• When the egg hits the pillow the time increases and the force decreases

• As the time increase, the force continues to decrease

### Momentum is Conserved

• This section focuses on multiple objects interacting

### Soccer Ball Example

• Q: How do the force exerted on ball A and the time interval compare with the force exerted on the ball B and its time interval?

• A: Forces are equal in magnitude and opposite in direction & time intervals are also equal.

### Soccer Ball Example

• Q: How would you calculate the change in momentum of each ball?

• A:The change in momentum of each ball is equal in magnitude but opposite in direction because P=F t

### Law of Conservation of Momentum:

The total momentum of all objects interacting with one another remains constant

regardless of the nature of the forces between the objects.

No! Only way for the final momentum to be zero is for the initial momentum to be zero! Initially both skaters would have to have the same momentum in opposite directions….

Momentum of the spacecraft & its fuel before the rockets are fired must equal the momentum of the two after the rockets are fired…

### Example #4 Conservation of Momentum

• Choose the formula: