At the National Physics Laboratory in England a measurement of the gravitational acceleration g was made by throwing a glass ball straight up in an evacuated tube and letting it return, as shown in the Figure. The time interval between the two passages across the lower level is equal to ?TL = 2.09 s. The time interval between the two passages across the upper level is equal to ?TH = 1.14 s.

The distance between the two levels is equal to H = 3.51 m. Calculate the magnitude of g.

Height Time