Question

What are the two action-reaction force pairs when a ball is hung by a string?

Describe the direction of each of the four forces and the objects that exert those forces. Include whether they are contact or noncontact forces.

Answer 1

When a ball is hung by a string, there are two action-reaction force pairs:

1. The force of the ball pulling down on the string is equal in magnitude and opposite in direction to the force of the string pulling up on the ball. The direction of the force of the ball pulling down on the string is downwards, while the direction of the force of the string pulling up on the ball is upwards. Both of these forces are contact forces.

2. The force of the string pulling down on the attachment point (such as a hook or a nail) is equal in magnitude and opposite in direction to the force of the attachment point pulling up on the string. The direction of the force of the string pulling down on the attachment point is downwards, while the direction of the force of the attachment point pulling up on the string is upwards. Both of these forces are contact forces.

In summary, when a ball is hung by a string, there are two action-reaction force pairs: the force of the ball pulling down on the string and the force of the string pulling up on the ball, and the force of the string pulling down on the attachment point and the force of the attachment point pulling up on the string.