- Consider a horizontal cross-section through the water at a height above the base, and with thickness .
- Work out the area of this cross-section in terms of , and hence its mass in terms of and .
- This mass of water is raised through a vertical height of feet. Find an expression for the work done, , when this happens.
- Write down an expression for , and hence, by integrating between and , evaluate the total work done.
Can you do this now? Let us know where you got stuck, if not.