An experiment is designed to measure the time it takes for a trolley to travel down a straight ramp of length 2.5 m inclined at an angle of 12∘ 12^\circ\,12∘ to the horizontal.
A student releases the trolley from rest at the top of the ramp and uses a manual stopwatch to record the time taken for the trolley to reach the bottom.
The average measured time is found to be consistently greater than the theoretical time calculated using a constant acceleration model of a=gsin(12∘)a = g \sin(12^\circ)a=gsin(12∘) with g=9.8 m s−2g = 9.8\text{ m s}^{-2}g=9.8 m s−2.
Suggest one reason why the student's average measured time is greater than the calculated value.