Presentation on theme: "Newton’s Third Law of Motion"— Presentation transcript:
1Newton’s Third Law of Motion No higher resolution availableNewton’s Third Law of MotionKey ConceptsWhat is Newton’s Third Law of Motion?How can you determine the momentum of an object?What is the Law of Conservation of Momentum?Key Terms:Momentum
2Newton’s Third Law of Motion If one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object “For every action there is an equal but opposite reaction”
3Action – Reaction Pairs Examples from bookGymnast pushes down on vaulting horse, the horse pushes him up and overKayak paddle pushes the water back, the water pushes the kayak forwardA dog pushes down on the ground, the ground pushes up on the dog causing it to leap into the airOther Examples…….
4oppositely directed force on the first one. If the example above Detecting MotionYou can’t always detect motion when paired forces are in action.If one of the pairs is much more massive, you will only see the less massive object moveExample – When you push down on the Earth, you won’t see the Earth move, only you jumping in the air
5Do Action – Reaction Forces Cancel? If 2 equal act in opposite directions they are balanced and cancel each other out. There is no movementAction – Reaction forces do not cancel out because they are acting on 2 different objects
6MomentumA characteristic of a moving object that is related to the mass and velocity of the objectCan be determined by the following formula”Momentum = mass X VelocityUnit is kg *m/sLike velocity and acceleration, momentum has a direction. Its direction is the same as its velocity
7Sample Momentum Problem Which has more momentum: a 3.0 kg sledgehammer swung at 1.5m/s, or a 4.0 kg sledgehammer swung at .9m/s?Mass 1 = 3.0kgVelocity 1 = 1.5 m/sMomentum = mass X velocity = 3.0kg * 1.5m/2 = 4.5kg*m/sMass 2 = 4.0kgVelocity 2 = .9m/sMomentum = mass X velocity = 4.0kg * .9m/s = 3.6kg*m/s
8Math Practice 1A golf ball travels at 16m/s, while a baseball moves at 7 m/s. The mass of the golf ball is .045 kg and the mass of the baseball is 0.14 kg. Which has greater momentum?
9Math Practice 2What is the momentum of a bird with a mass of kg flying at 15 m/s?
10Momentum The more momentum an object has the harder it is to stop The more mass an object has, the more momentum. You can stop a baseball traveling 20m/s, but not a truckThe greater the velocity an object has, the harder it is to stop. An arrow shot from a bow has a large momentum even though it has a small mass
11Conservation of Momentum Conservation – same amount before and after an eventTotal amount of momentum objects have when they collide is conservedLaw of Conservation of Momentum – states that in the absence of outside forces, the total momentum of objects that interact does not changeFriction is an example of an outside force