Determine an approximate value for the acceleration of free fall using a tennis ball, metre ruler and a stopwatch.

Drop the ball from a given height that is measured with the ruler and measure the time it takes for it to reach the ground using the stopwatch. Use the appropriate SUVAT equation of motion: we have a height (vertical displacement, acceleration only acts downwards due to gravity) and a time, and would like to calculate acceleration. Hence we need s = ut + 1/2 at², where "s" is the height from which the ball was dropped, "u" is initial velocity which is 0, "t" is the time of dropping and "a" is the acceleration which we would like to find out. Reorder the equation for "a": a=2*s/t² and substitute in the known values. Repeat this a few times and take an average due to measurement errors and for better reliability of the experiment.