Steel Sphere Acrylic Sphere A Length of Track (cm) (s) 80 cm 80 cm (Step 1, use 80 cm) B Angle of Elevation (0) in Degrees 20 20 (Step 1) C Calculated Time from s=0 to s=80 5.01 5.01 (formula from step 2) D Measured Time from s=0 to s=80 0.85 0.92 (step 3 with stopwatch) E % Difference (step 4) 143% 68.97% first value - second value percent difference = first value + second value x 100% 2