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Energy and Momentum
Energy, Momentum, Work, Conservation Laws, Collisions, etc
|Momentum is a (vector/scalar) quantity.
|Momentum is a vector, because it has both a magnitude and a direction.
|Momentum is defined by...
|Momentum is the product of the mass of an object and its velocity. ("Momentum")= ("Mass") X ("Velocity")
|What does "Momentum is Conserved" mean?
|Momentum stays the same within a system; in other words NO MOMENTUM IS GAINED OR LOST WITHING A SYSTEM.
|What is the net momentum (as a system) of a gun that is about to be fired, in an ideal situation; only concerning the gun and the bullet?
|ZERO, before the gun is fired, there is no momentum, since neither the gun, nor the bullet is in motion!
|What is the net momentum of a system in which a gun fires a bullet, if the system consists of both gun and bullet?
|ZERO, the momentum of both the gun and the bullet are equal (although it may be less apparent with the gun than with the bullet) and OPPOSITE! So, with momentum in OPPOSITE directions, they cancel each-other out, and it remains p = ZERO!
|Newton's Second Law justifies what about Momentum?
|The rate of change of the momentum of a particle is proportional to the resultant force acting on the particle and is in the direction of that force.
|What does "Momentum is a conserved quantity" mean?
|This means that the total amount of momentum in a closed system never changes. The momentum is "conserved" or transferred from one object to another. This happens in such a way that the total momentum of the system remains constant.
|Is Momentum conserved in a collision?
|Yes! The forces that act upon the system during a collision are all acting WITHIN the system.
|Situation: "Ball-A, moving at a constant velocity, strikes equally massive Ball-B, which is at rest. Ball-B then takes off with the very same velocity as Ball-A had to begin with, while Ball-A is now at rest." This collision was (elastic/inelastic).
|It was ELASTIC, because, while Ball-B may have gone at the same velocity as Ball-A began with, AFTER the collision, Ball-A stays behind and is at rest---- so they don't stick together.
|Situation: "Two balls meet in a head-on collision, and after the collision, both balls continue rolling--- but in the opposite direction of their original roll, and in the direction that the opposing ball WAS going. " The collision is(inelastic/elastic)?
|Elastic- they didn't stick together!
|When two balls begin with different velocities, but are moving in the same direction. What equation would you use to determine their velocity after collision, in an INELASTIC collision?
|Well, m<small>1</small>v<small>1</small>+m<small>2v<small/>2=(m<small>1</small>+m<small>2</small>)V<small>f</small> so...
|What is NOT conserved in an inelastic collision? a) Mass b) Energy c) Momentum d) KE
|Kinetic Energy is NOT conserved in an inelastic collision because it converts into heat etc.
|Two cars collide in a perfectly inelastic collision. The mass of car(1) is 1,090 kg and the mass of car(2) is 1,370 kg. What is the velocity of car(2) after the collision if the velocity of car(1) after the collision is 8.507m/s?
|If it's perfectly inelastic they'll both have the same speed after the collision.
|The product of force times distance is... a) KE b) PE c) work d) power
|c) work Work= fd Work= (force) X (distance)
|The rate at which work is done is called?
|If an object in motion possesses... a) KE b) PE c) Force d)Power
|a) Kinetic Energy
|Which of the following is true about an object with less acceleration than g? a) It is converting PE & KE into heat b) It is converting PE into KE & heat c) It is converting PE into heat only d) It is converting PE into KE only
|b) It is converting PE into KE and Heat.
|A light car and a heavy truck have the same KE. a) They have the same speed b) The car is going faster than the truck c) The truck is going faster than the car
|b) The car is going faster than the truck
|A car is traveling twice the speed of a truck. The car has half the mass of the truck. a) They have the same E b) Car has more KE c) Truck has more KE
|b) car has more KE
|Car A has twice the mass of Car B. Both begin at rest. Equal forces act on both for equal distances. In the end: a) Car A is moving faster b) Car B is moving faster c) Car A has greater KE d) Car B has greater KE e) Both cars are moving at same speed
|b) car B is moving faster
|ΔKE=? a) it's loss of PE b) total work done to it c) heat produced by motion
|b) total work done to it