The variable gravity

according to the question,

m=20kg

u=0m/s

h=5m

t=1s

a=g=?

now we know s=ut+1/2at^2 i.e. 5=a/2*1^2

                                2*5=a=10=g

thereby, work done =mgh=20 10 5=1000

We have ; m=20 kg ; s = 5m ; t = 1 s ; u = 0 Work done = mgh...............1 Now using , s=ut +1/2gt^2, we get 5=0+1/2g ;g=10m/s^2 Using 1 we get W=1000J

You shouldn't consider the given height. Because its mentioned that work done in 1s .

So work done $=mgh$ $=mg(ut+\frac{1}{2}gt^2)$ As the object is falling from the rest,

u=0m/s; t=1s; m=20kg; $g=10ms^{-2}$

Then you just plug them in the equation to get the 1000J answer!

I don't know any way of doing in without the g given!