Answer:
W=2001.24 newton meters
Caution: check units and arithmetic - I often make errors.
Step-by-step explanation:
Work is force times distance.
Denote height by h where h=0 is at ground level.
Denote the mass of the bucket and rope at height h by m(h).
The rate at which the bucket loses mass with height is (20-16)/10=0.4 kg/m
The rate at which the rope between the bucket and the top of the building loses mass is 0.4 kg/m
The initial mass of the bucket and rope is
[tex]m_{0}=20+0.4+0.4(10)=24.4[/tex]
The mass at height h is
[tex]m(h)=24.4-0.8h[/tex]
The force required at height h is
m(h)g
where g is the gravitational acceleration.
g=9.81 meters/sec/sec
The work required is
[tex]\int\limits^b_a {m(h)g} \, dh[/tex]
Where a=0 and b=10
[tex]g\int\limits^b_a {(24.4-0.8h)} \, dh=g(24.4h-0.4h^2)\left \{ {{10} \atop {0}} \right.[/tex]
g(244-40)=204g
W=2001.24 newton meters
