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Momentum and Inertia. 8SCIENCE. Matter in motion. Matter is what all things in the universe are made from – atoms etc. The amount of matter is called mass Usually in kilograms (kg) Mass is important:
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Momentum and Inertia 8SCIENCE
Matter in motion • Matter is what all things in the universe are made from – atoms etc. • The amount of matter is called mass • Usually in kilograms (kg) • Mass is important: • Objects with a lot of mass are hard to move and once they start moving, are difficult to stop • This ability to stay still or stay moving is called inertia
Momentum • Sir Isaac Newton was a scientist who developed the ideas of gravity and many laws of physics • He decided mass and velocityare the two most important factors to know when describing motion • He called this momentum: mass (m) x velocity (v) = momentum (p) m x v = p (momentum)
Momentum • Momentum includes velocity, which means it has a direction • ex: if a ball is hit from a tennis racket and coming towards you, you should move out of the way – even if you catch the ball, it will hurt your hand. This ball has momentum. • Momentum points in the direction of motion, and an object can have positive or negative momentum depending on the direction • Ex: What is the momentum of these balls? B
Conservation of Momentum • Law of conservation of momentum: • If no outside forces act on a group of objects, the momentum of the objects will never change • If an object slows down, its because it has hit another object and that hit object begins to move faster • Ex. Billiards: • When you hit the balls in a rack the main ball slows down when it hits the rest and the momentum is transferred, gaining an equal amount of momentum to travel across the pool table