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Momentum

Momentum. And its Conservation. Momentum is defined as mass times velocity. Momentum is represented by the symbol p, and is a vector quantity. p = m v momentum = (mass)( velocity) the SI units are mass & velocity combined (kg x m/s). Momentum. Bowling ball or basketball?.

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Momentum

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  1. Momentum And its Conservation

  2. Momentum is defined as mass times velocity. Momentum is represented by the symbol p, and is a vector quantity. p = mv momentum = (mass)( velocity) the SI units are mass & velocity combined (kg x m/s) Momentum

  3. Bowling ball or basketball? Picture two lanes at a bowling alley. One with a bowling ball the other with a basketball going at the same speed. Which will exert more force on the pins? Why? More momentum

  4. Momentum Example A 2250 kg pickup truck has a velocity of 25 m/s to the east. What is the momentum of the truck? p = mv p = (2250 kg)(25 m/s east) p = 5.6 x 104 kg x m/s to the east

  5. Momentum 2) A deer with a mass of 146 kg is running head-on toward you at a speed of 17 m/s. You are going north find the momentum of the deer. p = 2482 kg*m/s south

  6. 3) A 21 kg child on a 5.9 kg bike is riding with a velocity of 4.5 m/s to the northwest. • What is the total momentum of the child and the bike together? • What is the momentum of the child? • What is the momentum of the bike?

  7. Conservation ofMomentum So far we only have considered the momentum of only one object at a time. Now we will look at two or more objects interacting with each other. Picture this. . .You are playing pool. You strike the cue ball it hits the 8 ball. The 8 ball had no momentum before they collided. During the collision the cue ball loses momentum and the 8 ball gains momentum. The momentum the cue ball loses is the same amount that the 8 ball gained.

  8. Conservation ofMomentum The 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. total initial momentum = total final momentum p1i + p2i = p1f + p2f m1v1,i+ m2v2,i= m1v1,f+ m2v2,f

  9. Momentum is Conserved The total momentum of all objects interacting with one another remains constant regardless of the nature of the forces between the objects. Go back to the pool table example. The cue ball and the 8 ball do not have a constant momentum, but the total momentum is constant.

  10. Momentum is Conserved Picture this . . . Two people on skates facing one another. They push away from one another. Initially, they are both at rest with a momentum of 0. When the push away, they move in opposite directions with equal but opposite momentum, so that the total momentum is unchanged and still 0.

  11. Little Problem A 76 kg boater, initially A 76 kg boater, initially at rest in a stationary 45 kg boat, steps out of the boat and onto the dock. If the boater moves out of the boat with a velocity of 2.5 m/s to the right, what is the final velocity of the boat?

  12. Impulse In a collision of two ordinary objects, both objects are deformed, often considerably, due to the large forces involved.

  13. Impulse When the collision occurs, the force usually jumps from zero at the moment of contact to a very large value within a very short period of time, and then abruptly returns to zero again.

  14. Impulse From Newton’s second law, the net force on an object is equal to the rate of change of momentum: Multiplying both sides by t gives: Impulse = F x t = ρ = m x v

  15. Impulse Impulse helps us when dealing with forces that occur over a short period of time.  A golf ball being hit A water balloon catching contest ?  It should be noted that Impulse I = F x t Can be represented by the area under a graph of force vs time.

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