Question

What are two pairs of action reaction forces involving a bucket?

Answer 1

Hint:Consider two situations of the bucket when it is hand held above ground level and when it is kept at a surface, and deduce the forces acting on it for those positions of the bucket.

Complete answer:
 We know that the action reaction forces involving a motion are the forces which act in equal magnitude and in opposite directions between two bodies. Action-reaction forces are the contact forces acting on the body. Here, if the bucket is hand held then in this situation there are two forces acting on the bucket:
-Muscular force by the person holding it, acting upward on the bucket
-Gravitational force acting downwards on the bucket.

So, for this position of the bucket we can see that the pair of action-reaction forces acting are the Muscular force of the person and the gravitational force of the earth. Now, if the bucket is kept at a surface, there are two forces acting on the bucket:
-Gravitational force on the bucket acting downward on the bucket.
-Normal force by the surface in which the bucket is kept steady.

So, in this position of the bucket we can see that the pair of action –reaction forces acting are the normal force of the surface and the gravitational force of the earth.

Note:The action -reaction forces are always contact forces. Here we can see that due to the force by the gravitational field on the bucket, the bucket interacts with the hand of the holding person. In reaction to this force by the bucket due to gravitation the muscle of the hand gives a force opposite to it and holds the bucket in place. Similar case happens when the bucket is on a surface. The muscular force is only replaced with the normal force of the surface.