Hi The Legend, first we have to find the force i.e weight of the 4 kg by multiplying with g = 9.8 m/s^2 - the acceleration due to gravity
So weight = 4 * 9.8 = 39.2 N
Displacement made in the direction of weight 1.5 m.
Actually no need to do work against gravity. Because it goes to a level of lower potential
We can say that work is performed by gravity.
Work done = Force * displacement = 39.2 * 1.5 = 39.2 * 3/2 = 19,6 * 3 = 58.8 J
If suppose we take the same 4 kg mass upward through 1.5 m then we do work against gravtiy and the same amount 58.8 J will be performed
If we take g = 10 m/s^2 then 60 J of work will be performed