between a stone and the feather which would fall first in a chamber. won't it be the stone since the mass is heavier?

If there is no air resistance in the chamber, then both the stone and feather will fall at the same time.

 

This is because the time of fall or the distance travelled in the fall do not depend on the mass of the object.

 

This is evident from the three equations of kinematics:

 

1) v = u + at

 

2) s = ut + ½at²

 

3) v² = u² + 2as

 

However, if air resistance is present like there on Earth, then stone will fall first as the feather will be dragged by air.