Newton’s 1st and 2nd Laws

Newton In the 1660’s Sir Isaac Newton formulated three laws of motion. These laws describe how forces affect motion. All by the age of 18

Newton’s 1st Law An object at rest stays at rest and an object in motion stays in motion until acted on by an outside force. Nothing will begin moving or stop moving unless something makes it.

Inertia and the 1st Law Inertia is the property of an object that causes it to resist motion. The more mass an object has, the more inertia it has.

Newton’s 2nd Law The 2nd law is Force = mass times acceleration. F=ma Large force on a small mass gives large acceleration. Small force on a large mass gives small acceleration

A Newton The unit of force is called a Newton (N). 1N will accelerate 1kg at 1m/s2 After any force answer always put N for the units.

Practice with the 2nd Law A car has a mass of 1000 kg and is accelerating at 3m/s2. What is the force acting on the car? What force is need to cause a 3kg bowling ball to accelerate 4m/s2?

Newton’s 3rd Law For every action there is an equal and opposite reaction. Ex. Sitting in your chair. Gravity pulls you down and your chair pushes back with an equal and opposite force.

Rockets The action: Fuel is forced out of the back of the rocket. The reaction: The rocket is moved forward.

Momentum All moving objects have momentum. Momentum depends on the mass and velocity (speed) of an object.

Calculating Momentum Momentum = mass x velocity Momentum(P) = m x v Mass is measured in kg and velocity in m/s. Therefore the units of momentum are kg-m/s. This is said kilogram meters per second.

Practice with Momentum A bowling ball has a mass of 3 kg and travels with a velocity of 5 m/s. What is the momentum? A car weighing 1500 kg is traveling with a velocity of 4 m/s. What is the momentum?

Conservation of Momentum The total momentum is always conserved unless acted on by an outside force. Momentum is transferred from one object to another.

Examples of Conservation A bat hitting a baseball. The momentum is transferred from the bat to the ball. Bowling. The momentum is transferred from the bowling ball to the pins.