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MOMENTUM

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Like inertia, the momentum of an object depends on its mass ... You can use speed instead of velocity if you don't need to know the direction of ... Bumper cars... – PowerPoint PPT presentation

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Title: MOMENTUM


1
MOMENTUM
  • FORCES transfer MOMENTUM

2
What is Momentum?
  • Momentum is the measure of mass in motion.
  • Every moving object has momentum.

3
Momentum and Inertia
  • Momentum is similar to inertia
  • Like inertia, the momentum of an object depends
    on its mass
  • BUT, momentum also depends on how fast an object
    is moving!!!

4
Momentum has an equation!
  • Momentum mass velocity
  • p mv
  • units kg m/s

5
Momentum is a vector!
  • It has both
  • Size
  • Direction
  • Just like
  • Force
  • Velocity
  • Acceleration

6
So, what is its direction?
  • The direction of an objects momentum is the same
    as its...
  • VELOCITY
  • You can use speed instead of velocity if you
    dont need to know the direction of motion.
  • But, if you are working with more than one
    object, it is important to know the direction of
    momentum.

7
A question for you!
  • Q How do an objects mass and velocity affect
    its momentum?
  • A An increase in either mass or velocity
    increases momentum a decrease in either mass or
    velocity decreases momentum.

8
Calculating momentum!
  • Q What is the momentum of a 1.5 kg ball moving
    at 2 m/s?

9
Calculating momentum!
  • A
  • 1. What do you know?
  • Mass 1.5 kg, velocity 2 m/s
  • 2. What do you want to find out?
  • Momentum
  • 3. Write the formula
  • p mv

10
Calculating momentum (continued)
  • 4. Substitute into the formula
  • p 1.5 kg 2 m/s
  • 5. Calculate and simplify
  • p 3 kg m/s
  • 6. Check that your units agree
  • Unit is kg m/s
  • Unit of momentum is kg m/s (units agree!)

11
What happens when objects collide?
  • Q What is a collision?
  • A A collision is a situation in which two
    objects in close contact exchange energy and
    momentum.

12
What happens when objects collide?
  • Momentum can be transferred from one object to
    another!
  • Bumper cars
  • Car bumps youand the force pushes your car
    forward, because some of the momentum of that car
    behind you is transferred to your car.

13
What happens when objects collide?
  • Momentum is conserved!
  • The colliding objects make up a system, where the
    total momentum of both objects is unchanged by
    the collision!

14
Example
  • total momentum
  • mom 1 mom 2

15
Example
  • forces in collision

16
Example
  • total momentum
  • mom 1 mom 2

17
  • What is the overall momentum of
  • a system made up of a 1 kg ball
  • moving west at 2 m/s and a
  • 1.5 kg ball moving east at
  • the same speed?
  • What do you know?
  • What do you want to find out?
  • Write the formula.
  • Substitute into the formula.
  • Calculate and simplify.
  • Check that units agree.
  • Subtract or add?
  • Answer?

18
  • 1 kg m/s east

19
To Review
  • 1. Momentum is the measure of mass in motion.
  • 2. Every moving object has momentum.
  • 3. Like inertia, the momentum of an object
    depends on its mass.
  • 4. BUT, momentum also depends on how fast an
    object is moving!!!

20
To Review
  • 5. Momentum mass velocity
  • p mv
  • units kg m/s
  • 6. Momentum is a vector.
  • 7. The direction of an objects momentum is the
    same as its...VELOCITY.

21
To Review
  • 8. An increase in either mass or velocity
    increases momentum a decrease in either mass or
    velocity decreases momentum.
  • 9. Momentum can be transferred from one object to
    another!
  • 10. Momentum is conserved!

22
To Review
  • 11. For two objects traveling in the same
    direction, add the momenta of the objects to get
    the total momentum of the system.
  • 12. For two objects traveling in the opposite
    direction, subtract the momenta of the objects to
    get the total momentum of the system.

23
QUESTIONS?
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