- In the first law, an object will not change its motion unless a force acts on it.
- In the second law, the force on an object is equal to its mass times its acceleration.
- In the third law, when two objects interact, they apply forces to each other of equal magnitude and opposite direction.
Newton’s laws of motion relate an object’s motion to the forces acting on it. In the first law, an object will not change its motion unless a force acts on it. In the second law, the force on an object is equal to its mass times its acceleration. In the third law, when two objects interact, they apply forces to each other of equal magnitude and opposite direction.
The first law of motion states that an object will not change its speed or direction unless an unbalanced force affects it. Another name 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.
Examples of Newton’s 1st Law of motion
- If you slide a hockey puck on ice, eventually it will stop, because of friction on the ice. It will also stop if it hits something, like a player’s stick or a goalpost.
- If you kicked a ball in space, it would keep going forever, because there is no gravity, friction or air resistance going against it. It will only stop going in one direction if it hits something like a meteorite or reaches the gravity field of another planet.
- 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 of Motion
The second law of motion states that acceleration is produced when an unbalanced force acts on an object i.e. mass. The more mass the object has the more net force has to be used to move it.
Examples of Newton’s 2nd Law of motion
- 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 of Motion
The third law of motion states that for every action there is an equal and opposite reaction that acts with the same momentum and the opposite velocity.
Examples of Newton’s 3rd Law of Motion
- When you jump off a small rowing boat into the water, you will push yourself forward towards the water. The same force you used to push forward will make the boat move backward.
- 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.
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