Newton’s Laws of Motion

Learning Targets: Today students will learn : To identify Newton’s 3rd Law of Motion To define what momentum is To describe the relationship between momentum, mass, and velocity

Activity 1: “Say Something” After watching the following video clip, you will turn to your partner and discuss what you observed.

Activity 1: Does mass affect Newton’s 3rd Law?

Activity 1 : “Say Something” Now turn to your partner and discuss your interpretation of momentum. Does the mass affect the force exerted on an object at impact/collision?

Activity 2: Jot Notes Students will complete jot notes from Ch. 10 Sec. 4 – Newton’s 3rd Law Be sure to include all information in RED.

Newton’s Contributions to Science Calculus Light is composed of rainbow colors Reflecting Telescope Laws of Motion Theory of Gravitation

For every action there is an equal and opposite reaction. Newton’s Third Law For every action there is an equal and opposite reaction.

Newton’s 3rd Law For every action there is an equal and opposite reaction. Book to earth Table to book

Newton’s Third Law A bug with a mass of 5 grams flies into the windshield of a moving 1000kg bus. Which will have the most force? The bug on the bus The bus on the bug

Newton’s Third Law The force would be the same. Force (bug)= m x A Force (bus)= M x a Think I look bad? You should see the other guy!

Newton’s Third Law The force would be the same. WHY??? Bus = greater mass, greater inertia Bug cannot not change the inertia of the bus, but bug exerts same force on bus as bus on bug.

Newton’s Third Law The force would be the same. WHY??? Bus = greater mass, greater inertia Bug cannot not change the inertia of the bus, but bug exerts same force on bus as bus on bug.

Action and Reaction on Different Masses Consider you and the earth Action: earth pulls on you Reaction: you pull on earth

Action: tire pushes on road Reaction: road pushes on tire

Reaction: gases push on rocket Action: rocket pushes on gases

Momentum Momentum can be defined as "mass in motion." All objects have mass; so if an object is moving, then it has momentum - it has its mass in motion.

Variables that affect momentum The amount of momentum that an object has is dependent upon two variables: how much stuff is moving how fast the stuff is moving. Momentum depends upon the variables mass and velocity.  In terms of an equation, the momentum of an object is equal to the mass of the object times the velocity of the object.

Momentum equation Momentum = mass • velocity p = m • v where m is the mass and v is the velocity. The equation illustrates that momentum is directly proportional to an object's mass and directly proportional to the object's velocity.

Newton’s 3rd Law The more mass an object has the more momentum it has, so the harder it is to stop the object. Ex. A car moving 20 m/s is harder to stop than a baseball moving at 20 m/s because the car has a greater mass and greater momentum.

Examples 1. Determine the momentum of a ... 60-kg halfback moving eastward at 9 m/s. b. 1000-kg car moving northward at 20 m/s. c. 40-kg freshman moving southward at 2 m/s

Law of conservation of Momentum In a closed system, the loss of momentum of one objects equals the gain in momentum of another object – momentum is CONSERVED

What is Law of Conservation of Momentum?

Conservation of momentum problems 1. In a collision, a 5 kg mass moving at 30 m/s transfers all of its momentum to a 15 kg mass. What is the velocity of the 15 kg mass after the collision?

Conservation of momentum problems Advanced only! 2. A 15 kg mass moving at 15 m/s collides with a stationary 12 kg mass. After the collision, both the 15 and the 12 kg mass move off in the same direction. If the 12 kg mass is moving at 5 m/s, what is the speed of the 15 kg mass? 3. An 18 kg mass moving at 8 m/s collides with a 16 kg mass moving in the same direction at 6 m/s. After the collision, both the 18 and the 16 kg mass continue to move in the same direction. If the 18 kg mass is moving at 5 m/s, what is the speed of the 16 kg mass?

Review Newton’s First Law: Objects in motion tend to stay in motion and objects at rest tend to stay at rest unless acted upon by an unbalanced force. Newton’s Second Law: Force equals mass times acceleration (F = ma). Newton’s Third Law: For every action there is an equal and opposite reaction.