People use a variety of methods to wash clothes. Usually after adding the soap, they beat the clothes on a stone, or beat it with a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes ?

It is necessary to agitate to get clean clothes because the soap micelles which entrap oily dirt on the surface of dirty cloth have to be removed from its surface. When the dirty clothes are agitated in soap solution, the oily dirt particles entrapped by soap micelles get dispersed in water and the clothes get cleaned.