Newton’s 3 Laws of Motion

Newton’s first LawNewton’s first LawThe Law of InertiaThe Law of Inertia

• An object Stays in the state of rest or motion unless acted on by another force

• This law explains why a driver is thrown forward in a head-on automobile accident. The car may have stopped, but the driver continues moving forward unless held in place by a seatbelt.

Newton’s 2Newton’s 2ndnd Law LawThe Law of AccelerationThe Law of Acceleration

• When a force acts on an object, the object will accelerate proportionally to the force and in the same direction.

• To understand this law, imagine pushing a pebble, and then imagine pushing a boulder.

• The pebble has a smaller mass, and so it will accelerate faster than the boulder if the force is the same .

Vs.

• Now imagine pushing a boulder with your bare hands and then imagine pushing it with a powerful backhoe.

• The backhoe is able to exert more force on the boulder, and it will make it accelerate faster than when you pushed it with your bare hands.

Vs.

As long as the force remains constant, an object with a smaller mass will

accelerate faster.

As long as the mass remains constant, acceleration will be faster

with a greater force.

AND

Newton’s 3Newton’s 3rdrd Law LawThe Law of InteractionThe Law of Interaction

• For every action, there is an equal and opposite RE-Action.

•A baseball is thrown towards the batter at a certain force.

•The batter then places the bat in the path of

the ball.

• The Ball hits the Bat in the

direction it was thrown.

•The force is returned equally in the opposite direction by the

bat.

•This causes the ball to travel into the playing field.

•Why do some balls travel farther then

others?

Newton’s Collisions - Example #1• Two bumper cars are in a high velocity head-on

collision. Each car has a mass of 300 kg.• The red car has a person with a mass of 25 kg.

The red car is at rest.

• The green car has a person with a mass of 75 kg.

What’s going to happen?

A B

• Because the red car was sitting still and was hit by a car traveling at a high rate of speed with a driver three times the mass, the red car will experience the greatest change in position.

• After the collision, the red car will move off with the green car in the direction the green car was moving.

Newton’s Collisions - Example #2• Two bumper cars are in a glancing collision.

Each car has a mass of 300 kg.• The red car has a person with a mass of 90 kg.• The green car has a person with a mass of 45

kg.• Both cars are traveling at the same velocity.

What’s going to happen?

A B

• The driver of the red car has twice the mass of the driver of the green car, and they are traveling at the same speed.

• When they collide, the red car will slow down and the green car will speed up.

• They will both be deflected from their original path, but the red car will be deflected less than the green car because of the greater mass.

Newton’s Collisions - Example #3• Two bumper cars are in a head-on collision.

Each car has a mass of 300 kilograms.• The red car has a person with a mass of 70 kg.• The green car has a person who also has a

mass of 70 kg.

• The red car has a velocity twice that of the green car.

What’s going to happen?

A B

• In this head-on collision with cars of equal masses, the red car will end up exchanging velocities with the green car.

• This will cause the green car to be deflected at a greater velocity than the red car.

• Both cars will be deflected back along their previous paths.