MOMENTUM

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MOMENTUM

• FORCES transfer MOMENTUM

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What is Momentum?

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

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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!!!

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Momentum has an equation!

• Momentum mass velocity
• p mv
• units kg m/s

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Momentum is a vector!

• It has both
• Size
• Direction
• Just like
• Force
• Velocity
• Acceleration

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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.

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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.

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Calculating momentum!

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

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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

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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!)

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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.

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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.

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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!

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Example

• total momentum
• mom 1 mom 2

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Example

• forces in collision

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Example

• total momentum
• mom 1 mom 2

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• 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?

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• 1 kg m/s east

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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!!!

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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.

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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!

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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.

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QUESTIONS?