Question

on moon man feels lighter than earth ?why.

Answer 1

How much a man weighs depends on the gravitational force with which you are attracted. The gravitational force on moon is 1/6 times the gravitational force on earth. Since the gravitational force is less, the man feels lighter on moon.

Answer 2

   A  person feels lighter or heavier based on the normal reaction force exerted by the floor he/she stands on.  The weight of the person is the force the person exerts on the floor.  This force is due to the gravitational attraction force (Newtons' law).

   
       force = G M m / R²
           G = Universal Gravitational constant,  M mass of planet  (Earth or Moon)
            R = Radius of planet.          m = mass of the person.

       the ratio  M / R² is more on Earth  than  on Moon.  It is around  6 times.. So a person weighs less on the Moon.  The mass of the person is the same on both planets.