### A physicist’s merry-go-round

• What can you do here
1. Stand on the rim of the still merry-go-round. Start walking along the circumference. What is happening? Stop. Change the direction of your movement. What are you noticing?
2. Stand on the rim of the merry-go-round. Ask someone to make it turn. Note the stance you have to adopt to remain on the platform.
3. When the merry-go-round is moving try to walk across it, along the diameter. Is that easy?

• How does it work
1. When you walk in one direction, the merry-go-round is spinning in the opposite way. It happens because of the law of conservation of angular momentum which depends on the mass, size, and angular velocity of the physical system and whose value is always 0 unless an external force is applied to the system.
2. To keep your balance on the rotating platform, you have to lean over towards its centre. This makes all forces acting on Your body are balanced, also centrifugal force, which is trying to throw away You from the platform.
3. Walking along the diameter of the rotating merry-go-round is difficult due to the Coriolis force in the system, which acts on us in the direction perpendicular to the path of movement.

• Interesting facts
The Coriolis force is responsible for the direction of winds blowing in the tropics, the so-called trade winds. They had considerable importance in the age of sail.