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Newton's 3rd Law of Motion
Terms in this set (10)
Bart Simpson fire extinguisher scenario:
What do you notice about the direction of the force and Bart's resulting motion?
Bart pushes the fire extinguisher forward, but the resulting force pushes him backwards. This is an example of Newton's 3rd Law. When Bart applies the force forwards, there is an equal reaction force that sends him backwards.
Newton's 3rd Law
- For every action there is an equal and opposite reaction
- For each force there is an equal, opposing force
- For every action force, there is an equal and opposite reaction force
(forces are always paired)
Examples of Newton's 3rd Law
- When a cannon is fired, it fires in one directions but then goes backwards as there is an equal, opposing reaction force
- When a truck hits a pole, as even though the truck may move faster and send the pole flying--as the pole has less mass, NEWTON'S 2nd Law
- When a bowling ball hits the pins
- Bart Simpson when he goes backwards after opening a fire extinguisher
- When someone jumps off a boat, exerting a normal force but sending the boat backwards causing it to tip over (forces = weight, downward force and buoyancy, upward/normal force)
- A car driving on the road
- When rockets and other projectiles are launched
Forces come in...
action-reaction force pairs
How does Newton's 3rd Law affect walking on the floor?
- A person walking is putting a force down and back against a floor but doesn't sink through it because the floor exerts a push back up and forward on her foot.
- Because the floor's force upward isn't any greater than the force the person puts down on it, they don't go flying up into the air
How are Newton's 2nd and 3rd Laws related?
- When two objects interact, they apply forces to each other of equal magnitude and opposite direction.
- However, due to the mass of the objects, sometimes one will move--and if the object has less mass, it will have more acceleration.
- This can be seen when a truck hits against a pole. At first, the forces each object exerts against each other will be the same, but the pole's smaller mass means that it will be affected more, and it will move more.
Forces are always
- no force exists by itself
- there is always an action force and a reaction force
Other examples of Newton's 3rd Law
- Rockets leaving Earth
- Guns being fired
- Two cars hitting head on
- Jumping out of a boat onto the dock
A rocket works by propelling ________ out of the back end at high ____________. The ___________ of the mass of the burning fuel accelerating out the back end applies an _____________ reaction force to the rocket, moving it upward. The rocket is not simply pushing against the ground.
When two people collide, what happens?
- The two people exert a push force against each other (same force)
- One can fall because according to Newton, when two objects with unequal mass collide, they will accelerate at different rates.
- The object with smaller mass will accelerate more, even though each one is affected by the same force.
- If each object has the same mass, then they will accelerate at the same speed
- They press against each other with equal force in opposite directions
THIS SET IS OFTEN IN FOLDERS WITH...
Unit 1 Vocab Review
Newton's 1st Law
Newton's Second Law of Motion
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