Kinematic pairs according to the type of closure

 Kinematic pairs according to the type of closure:

According to the type of closure between the elements, kinematic pairs can be classified as 1. Self closed pair, 2. Force closed pair

1. Self closed pair: 

In a self closed pair, two elements of the pair are mechanically connected in such a way that only specified relative motion occurs

All lower pairs are self closed pairs

2. Force closed pair: 

In a force closed pair, two elements of the pair are not connected mechanically but are kept in contact by the action of external forces.

A cam and follower is an example of a force closed pair, as the cam and follower are kept in contact by the force exerted by spring