Question

Name the forces acting on a plastic bucket containing water held above ground level in your hand. Discuss why the forces acting on the bucket do not bring a change in the state of motion.

Answer 1

Hint: Draw an FBD diagram of all the forces acting on the plastic bucket. Now, check if there is any acceleration in any direction. If not, the forces do not cause any change. But if anyone of the forces is removed, automatically the other will cause a change in motion.

Complete step by step answer:
The forces acting on the bucket are shown below with the help of a free body diagram.

Only two forces are acting on the bucket:
1. Gravitational force in a vertically downward direction
2. Muscular force by the hand (say Normal force) in a vertically upward direction.

Until the forces are in equilibrium, there is no such change in the state of motion. It is not mentioned, that the person is moving, or the bucket is moved in any of the directions, so the forces maintain equilibrium.
There may be a chance that the person might get fatigued by holding the bucket, and release the bucket, causing the removal of muscular force. Therefore, only gravitational force will be acting and hence the bucket might move downwards.

Note:
Always remember that the change in the state of motion is caused only if there is any acceleration applied. Unless the forces are always in equilibrium. So, the situation when the muscular force is removed, we have an acceleration due to gravity in a downward direction, causing the bucket to move downward.