Newton’s Laws of Motion

Laws of Motion Objects are in motion everywhere around us from molecules to planets Force puts these objects in motion (force = a push or a pull) All objects obey 3 laws of motion Laws of Humans vs. Laws of Nature

Background: Sir Isaac Newton Physicist, mathematician, astronomer, natural philosopher, alchemist Principia Mathematica (1687) 3 ed. -Universal Gravitation -3 Laws of Motion -Affirmed heliocentrism -Affirmed Kepler’s laws -Dominated scientific thinking then (apart of the scientific revolution) and now

Newton’s Three Laws of Motion 1st law says: Any object at rest, or in motion, will continue in that state unless acted upon by an external force In other words: An object in motion will remain in motion An object at rest will stay at rest

1st Law of Motion aka The Law of Inertia aka The Law of Inertia A) An object will keep moving in a straight line until something can stop it. (Unbalanced Force) B) Or will stay still until something can get it to move. No force, no acceleration. (Balanced Force) Examples: A hockey puck on ice A tee shot in space aka The Law of Inertia A) An object will keep moving in a straight line until something can stop it. (Unbalanced Force) B) Or will stay still until something can get it to move. No force, no acceleration. (Balanced Force) Examples: A hockey puck on ice A tee shot in space

Newton’s Three Laws of Motion 2nd Law says: The net force of an object is equal to the product of it’s acceleration and it’s mass In other words: Force = Mass x Acceleration FMA Triangle

2nd Law of Motion Example A 1,300kg Ferrari accelerates 31m/sec F = M x A F = 1,300kg (x) 31m/sec F = 40,300N 1N = 1kg/m/sec²

Newton’s Three Laws of Motion 3rd Law says: 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 In other words: for every action there is an equal and opposite reaction This is called the action reaction law

3rd Law of Motion Example: Notice the man standing in his boat, say he wants to step into the other boat What will happen when he reaches his leg out for the second boat? His leg will force his own boat backwards and he will fall in the water between the two boats!

Summary Sir Isaac Newton published his work on the 3 Laws of Motion in Principia Matematica -Newton gave credit to Galileo on 1st law (inertia) These three laws “govern” all, and any, object in motion no matter how big or small The three laws can overlap This thinking has been proven scientifically and revolutionized the practice of science for the past 300 years

Which Law is It? A satellite is said to get a “free ride” in space. Once it is placed in orbit it will rotate around Earth without the need of a rocket to propel it. A car is driving down the road. It’s wheels make contact with the road’s surface. As the wheels roll forward the ground is pushed backward. 1st 3rd

Which law is it? A Car is traveling down route 33. Suddenly, it is hit by another car who has run the red light. A rocket ship waits for the countdown to be complete and take-off. 3rd 1st

An airplane weighing 5 tons accelerates down the runway at 30m/sec. As a car is hit by another, the people inside the car continue to move in the direction the car was moving. 2nd 1st

Two sumo wrestlers begin to push a school bus down the road Two sumo wrestlers begin to push a school bus down the road. After pushing the bus for 50m, the bus is traveling 5km/hr. Steve sees a deer on the edge of his property. He reaches for his 12 gauge shotgun. The gun fires the bullet and recoils back into Steve’s arm 2nd 3rd