# Newton’s 3 rd Law - PowerPoint PPT Presentation

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Newton’s 3 rd Law. Physical Science Section 3.3. Newton’s third law of motion when 1 object exerts a force on a 2nd object, the 2nd object exerts a force that is equal in size and opposite in direction to the force from the 1st object For every action, there is an equal & opposite reaction

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Newton’s 3 rd Law

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## Newton’s 3rd Law

Physical Science Section 3.3

• Newton’s third law of motion

• when 1 object exerts a force on a 2nd object, the 2nd object exerts a force that is equal in size and opposite in direction to the force from the 1st object

• For every action, there is an equal & opposite reaction

• Swimming- swimmer exerts force on water; water exerts force on swimmer

• Action-reaction pairs act on different object

• Rocket engine- rocket engine exerts force on the hot gases produced by the fuel

• gases exert a force on the rocket and push it forward

### Newton’s 3rd Law

• Orbit of earth in space influenced by:

• gravitational forces between the Sun and the Earth and between other planets and the Earth

• Discovery of Neptune

• Orbit of Uranus could not be explained by the planets known at the time

• Bicycle’s easier to stop than a car- less mass

• Less mass = less inertia and less momentum

• Object with less speed = less momentum

• Less speed = easier to stop

• Momentum- product of mass and velocity- influences how easily an object can be stopped

• P = m x v

• P : momentum Units kg*m/s2

• Has direction because velocity has direction

• Indicate direction of momentum

• Force can be calculated by using the final and initial momentum when an object changes its velocity.

• F = (mvf – mvi)/t)

• Law of conservation of momentum- total momentum does not change in a collision

• Momentum before collision = momentum after collision

• 2 objects collide when moving in the same direction

• first object slows and the second speeds up in the same direction

• 2 objects collide when moving in opposite directions with the same momentum

• Start with 0 momentum, collide, bounce off in opposite directions, still have 0 momentum