The light turns green, and the car starts to move quickly. You feel as if a big, invisible hand pushes you back in the car seat. When the car stops quickly, the same “hand” seems to push you forwards.
What is this invisible “something” that pushes you when a car starts and stops? It’s called inertia.
Inertia is the name for the way things resist a change in movement. When something is stopped, it stays stopped. It starts to move only when a force – a push or a pull – makes it move. And when something is moving, it tries to keep moving. It won’t stop until a force stops it.
When a car starts to move, your body tries to stay stopped. So you feel yourself pressing back as the car seat moves forwards. And when the car stops, your body tries to keep moving. Inertia “pushes” you forwards. Your seat belt is there to hold you back.
Use a whirling egg to see the force of inertia. Let a fresh egg warm up to room temperature. Then place the egg in a bowl. Gently spin the egg by pushing it with your finger. Stop the egg from spinning by touching it lightly on the top. Then quickly lift your finger from the egg. What happens?
The egg starts spinning again. Why? When you start the egg spinning, the liquid inside the shell spins, too. When you stop the egg, inertia makes the liquid inside keep spinning. When you let go of the egg, the spinning liquid makes the egg start spinning again.
Picture Credit : Google