Newton’s Laws

Newton’s 1st Law

The first law of motion sates that an object will not change its speed or direction unless an unbalanced force (a force which is distant from the reference point) affects it. Another name for the first law of motion is the law of inertia. If balanced forces act on an object it doesn’t accelerate or change direction. This means it doesn’t change its velocity and it doesn’t have momentum.

Example: If you are driving in your car at a very high speed and hit something, like a brick wall or a tree, the car will come to an instant stop, but you will keep moving forward. This is why cars have airbags, to protect you from smashing into the windscreen.

Newton’s 2nd Law

The second law of motion states that acceleration is produced when an unbalanced force acts on an object (mass). The more mass the object has the more net force has to be used to move it.

Examples: If you use the same force to push a truck and push a car, the car will have more acceleration than the truck, because the car has less mass. It is easier to push an empty shopping cart than a full one, because the full shopping cart has more mass than the empty one. This means that more force is required to push the full shopping cart.

Newton’s 3rd Law

The third law of motion sates that for every action there is a an equal and opposite reaction that acts with the same momentum and the opposite velocity.

Example: When you jump off a small rowing boat into water, you will push yourself forward towards the water. The same force you used to push forward will make the boat move backwards. When air rushes out of a balloon, the opposite reaction is that the balloon flies up. When you dive off of a diving board, you push down on the springboard. The board springs back and forces you into the air.