Newton’s Third Law

Vocabulary Review Inertia: the tendency of an object to resist changes in its state of motion Acceleration: a change in velocity a measurement of how quickly an object is changing speed, direction or both Velocity: The rate of change of a position along a straight line with respect to time Force: strength or energy

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

Newton’s Third Law a force on the chair a force on your body These two forces are called action and reaction forces.

Newton’s Third Law Action-Reaction Pairs- They act on different objects The rocket exerts a downward force on the exhaust gases. The gases exert an equal but opposite upward force on the rocket. FG FR

Newton’s Third Law When you sit in your chair, your body exerts a downward force on the chair and the chair exerts an upward force on your body.

Newton’s Third Law Flying gracefully through the air, birds depend on Newton’s third law of motion. As the birds push down on the air with their wings, the air pushes their wings up and gives them lift.

Why does it hurt so much when you stub your toe? When your toe exerts a force on a rock, the rock exerts an equal force back on your toe. The harder you hit your toe against it, the more force the rock exerts back on your toe (and the more your toe hurts).

Let’s see an example. ACTION: Rocket Gases push DOWN on air. REACTION: Air pushes up on rocket.

Try this one: REACTION: Air pushes UP on wings. ACTION: Wings push DOWN on air. REACTION: Air pushes UP on wings.

…And another! ACTION: Feet push back on the floor. REACTION: Floor pushes forward on feet.

Man push Up on weight bar ACTION: Man push Up on weight bar REACTION: Weight bar push downward on him

1st period have to turn in. 2nd per did not get to it

Assignment Summarize Newton’s Third Law of Motion in 10 words or less. Provide two examples of Newton’s Third of Law of Motion and explain each example. DO NOT use same examples from the powerpoint, book, or videos. Examples must be original.

Momentum A moving object has a property called momentum that is related to how much force is needed to change its motion. The momentum of an object is the product of its mass and velocity.

Momentum is given the symbol p : The unit for momentum is kg · m/s. Notice that momentum has a direction because velocity has a direction.

Law of Conservation of Momentum The momentum of an object doesn’t change unless its mass, velocity, or both change. The law of conservation of momentum- momentum can be transferred from one object to another Momentum is not lost or gained

Law of Conservation of Momentum This means that when two objects collide the total momentum of the objects before the collision is the same as the total momentum of the objects after the collision.

When Objects Collide The results of a collision depend on the momentum of each object. When the first puck hits the second puck from behind, it gives the second puck momentum in the same direction.

The Third Law of Motion 3.3 When Objects Collide If the pucks are speeding toward each other with the same speed, the total momentum is zero.

Title : The 3rd Law of Motion worksheet Write the questions. Draw the pictures Do not have to turn it in, keep in notebook for notebook quiz/notebook check

Exit Ticket Write Newton’s 3rd Law in your own words. What is the equation to find momentum? What is the momentum of a 7 kg car moving at 20 m/s?