When we spin ourselves round and round and then stop why do we feel dizzy?

1. The fluid in your inner ear continues moving after the rest of you stops.

2. Your brain attempts to compensate for long periods of motion by helpfully subtracting it. So if you're sitting on a window seat of an airplane, when the plane stops, it looks like the landscape is sliding backward because your brain is subtracting motion which is no longer there.

You have fluid inside your ear that lets your body know you're standing upright and help you keep your balance. When you spin, the fluid in your ear begins to swirl. When you stop, although your body has stopped moving, the fluid in your ear will continue to swirl for a few moments which affects your body making you dizzy.

Spin a raw egg in the shell then stop it quickly while it's spinning and let go of it. The egg will start spinning again on it's own because the liquid inside is still moving.

Or just swirl some water in a glass then stop swirling. The water in the glass will keep swirling.