if the surface is frictionless, the acceleration of the object=(mgsin?)/m=gsin?.....this is uniform acceleration
so after 5 sec, the velocity of the person will be after starting from rest at the top point:....fromn 1st eq of motion:
v=0+gsin? x t
now if the mass of another object is 70 kg in that case also the acceleration will be same as it is independent of the mass of the objkect. It is only dependent on the angle of inclination.