"Bucket Power" Return to list of pracs

Aim: This is to demonstrate the effect of inertia on motion of water in a bucket.

Equipment: The equipment includes...  

• bucket;
• water.

Method: Half fill a bucket with water and hold the bucket down by your side. Then swing the bucket up and around over your head down and up again. Why doesn't the water come out of the bucket when it is upside down?

Background knowledge: The spinning effect allows the water to remain in the bucket. The water in constantly being accelerated outwardly therefore preventing the water from falling out when the bucket it upside down above your head. Do you feel like you fall into the corner when you are in a car and travelling around a corner? Are you pushed outwards when sitting on a Merry Go Round? The faster the bucket swings the more force you experience. There will be a minimum speed that you need to swing the bucket in order for the water to remain in the bucket.

Theoretically, this speed must be a value so that the forces are equal and opposite to the acceleration that gravity creates on any object (ie. 9.8 metres per second every second). This means that any object at the surface of the earth speeds up by 10 metres every second (ie. 36km/h) every second. You can try it with your class. Get them to try to swing the bucket slightly slower each time but still make sure the water remains in the bucket. If you want further mathematical explanation to this please contact me.