Manu took a pebble and a sheet of paper both weigh one gram. His friend told that if we drop both at the same time, the pebble will fall straight to the floor, while the paper will slowly drift to the ground. Do you think friction have any role in this case? How can we relate that to the topic which we are learning today?

friction has no role to play in this case. because friction usually occurs between to parts which come in contacts. examples (a)our joints in the human body (b)two mechanical parts (shafts).

Explanation:

However what this topic relates to is gravity. The pebble and paper both weigh one gram, but have different density this is the sole reason why if both are drop from same height the pebble would reach the ground faster than the paper because it is more denser. unlike the paper with a lesser density which would take a longer time to reach the ground.

the body's situation won't change the forces are equal opposit and on the same body

no. dot product   =0 when vecs at right angles