A spring balance works on the principle of :

1. gravitational force
2. magnetic force
3. restoring elastic force
4. frictional force

A horizontal spring with two object A and B attached to its ends are shown in the figure below. If the spring is compressed, it …………… each object and if it is stretched, it …………… each object.

1. pushes, pulls
2. pulls, pushes
3. pushes, pushes
4. pulls, pulls

Define a non-contact force.

Classify the following amongst contact and non-contact forces —

(a) frictional force, (b) normal reaction force, (c) force of tension in a string, (d) gravitational force, (e) electrostatic force, (f) magnetic force.