A glider on an air track carries a flag of length l through a stationary photo gate, which measures the time interval ?td during which the flag blocks a beam of infrared light passing across the photo gate. The ratio vd l / ?td is the average velocity of the glider over this part of its motion. Suppose the glider moves with constant acceleration.
(a) Argue for or against the idea that vd is equal to the instantaneous velocity of the glider when it is halfway through the photo gate in space.
(b) Argue for or against the idea that vd is equal to the instantaneous velocity of the glider when it is halfway through the photo gate in time.