Question

in case of a body rolling down an incline does the normal force always passes through its centre of mass? if not why does it does in cases it does? and also for a sliding body what happens?

Answer 1

Yes if the mass of the body is evenly distributed about the geometrical centre. That is, if the geometrical centre and the centre of mass coincide.

Answer 2

but why does it passes through that point ?

Answer 3

in case of a cubical box sliding down the incline uniformly the normal force does not pass through the centre of mass right?
so why isn't it passing through the centre of mass now ?

Answer 4

so if moving uniformly net torque should be 0 around centre of mass.therefor there should a torqe provided by normal force to balance the torque by friction..so normal force does not pass through the centre of mass right?

Answer 5

The normal force does not, but the overall contact force (normal + friction) does. Because torque about any point (including centre of mass) must be zero.