ഫിസിക്സ് അദ്ധ്യാപകന്‍

A RIDDLE

In some situations , I oppose the motion


in other situations, I facilitate the motion

but , I always oppose

the relative motion

between two moving surfaces.

Put some lubricant , and

I become small there.

Make the moving surfaces rough,

I make the movement tough ,

I may be-

static, sliding or rolling

but whenever two surfaces are in motion

I am always there.

Tell me who I am!