Solve this:

A person of mass M kg is standing on a flits. If the lift moves vertically upwards according to given v-t graph then find out the weight of man at the following instants : (g-10 m/s²)

(i) t = 1 second
(ii) t = 8 second
(iii) t = 12 second

Find the acceleration of the system and the contact force between
(i) 2kg and 3 kg blocks (ii) 3kg and 5 kg blocks. 

If lift has an upwards acceleration, person weight will be m(g-(-a)) = m(g+a). Person will feel heavier.

If lift has a downward acceleration, person weight will be m(g-a) . Person will feel lighter.

When the elevator is moving at a constant velocity, Person weight will be mg.
(I) t = 1 sec
a = 10/1c= 10m/s² 
W'= m(g+a) = M(10+10) =20M

(II) t =8 sec
a = 0
So Weight W = mg = 10g

(III) T = 12 sec
a = -10 m/s²
W' = m(g-a) = 0

Kindly post different questions in different threads.

Regards