How to solve this ,

         A man is drawing water from a well using a bucket which leaks uniformly.When full the bucket weighs 20 kgs.after it reaches the top its weight is 10kgs.The depth of the water in the well is 20 m.Find the work done.

                                                     The answer is 3000J and i think it is correct.iam not getting the answer

 

 

As the water is leaking uniformly out of the bucket.

 

So the mass of the bucket is varying uniformly w.r.t height 'h'

 

If we plot the curve for force (along y-axis) versus height (or displacement along x-axis). Then area under the curve is the work done

 

Here area under the curve will be = (1/2) base*altitude

 

or W = (1/2)*(20m)*(20g-10g)N = 100g Joules = 1000 Joules