Newtons Laws of Motion

Isaac Newton

Isaac Newton was an English Scientist

In 1667, he developed 3 laws of motion that describe movement of objects in terms of forces

We still use these 3 laws of motion to this day

Newtons 1st Law of motion

An object moving at constant velocity keeps moving at that velocity unless an unbalanced net force acts on it.

• Newtons 1st Law of motion is often called the law of inertia
• All objects will just keep on doing what they are doing unless it is acted on by an unbalanced force
• All object resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will maintain this state of motion
The ball is a resting object until the person applies force which makes the ball a moving object. The ball will keep moving until a force stops the object, once the ball hits the wall the wall will stop the moving ball. This is an example of newtons 1st law.
This law is the same reason why you should always wear your seat belt because if you hit the brick wall without wearing your seat belt you will fly forward
Newton's 1st Law of Motion -Music Video

Newtons 2nd Law of motion

the acceleration of an object is in the same direction at the net force on the object, and that the acceleration equals the net force divided by the mass.
Acceleration(in meters/second sq) = net force (in newtons) / mass (in kilograms)

• The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass
• F = ma
• Force = Mass x Acceleration
• Units:
1. Force = newtons or kg m/s sq
2. Mass = Kilograms
3. Acceleration = m/s/s or m/s sq

practice problem

Mike's car, which weighs 1,000 kg, is out of gas. Mike is trying to push the car to a gas station, and he makes the car go 0.05 m/s/s. Using Newton's Second Law, you can compute how much force Mike is applying to the car.

F=1,000kg x 0.05m/s/s

You push the car with a force and the car will move forward or accelerate. If you push a car with more mass and push the car with the same force the car will still move forward or accelerate but the car will not move as far or have less acceleration.
Newton's Second Law of Motion

Newtons 3rd Law of Motion

When one object exerts a force on a second object, the second object exerts a force on the first object that is equal in strength and in the opposite direction

• This means that for every force there is a reaction force that is equal in size, but opposite in direction. That is to say that whenever an object pushes another object it gets pushed back in the opposite direction equally hard.

Another example of Newtons 3rd Law of motion is when you are walking on the sidewalk you are pushing on the ground and the ground is pushing back up on you. With every action there is an opposite and equal reaction.

The rocket's action is to push down on the ground with the force of its powerful engines, and the reaction is that the ground pushes the rocket upwards with an equal force.

Bill Nye and Newton's Third Law

Newtons 3 laws of motion

1st law-an object in motion will stay in motion unless acted upon by an outside force

2nd law-the acceleration of an object will stay in the same direction as the net force on the object ( A= F/M)

3rd law- When an object exerts a force on the first that is equal in strength and opposite in direction

In this picture newtons first law is explained because the ball will keep moving unless the ball gets stopped by an outside force. The second law is explained because there is force pushing on the ball and the ball is accelerating because the force is pushing on the ball. The third law is explained because two equal forces are pushing on back on each other.
Newton's 3 (three) Laws of Motion