Water Tank
A cylindrical bottle contains 900 ml of water. At t=0 a hole is punched in the bottom, and water begins to flow out.
It takes exactly 100 seconds for the tank to empty. Draw the graph of the amount of water z in the tank against time t. Explain the shape of the graph. Now do an experiment and collect and plot the data. Basic principles of physics tell us that the graph should be a parabola. Verify that this is the case. [There is a neat way to change variable so that your points should lie in a straight line.]