Physics Pre-Lab Help?????

Question

1. In your own words, describe how a photogate works.

2. A cart with a 5-cm-long flag on it passes through a photogate with a constant velocity of 10 m/s, how long does it take for the flag to pass through the photogate? (explain your reasoning) 

3.Pete and Angelica measure the speed of a car to be 10.2 ± 0.1 m/s and 9 ± 1 m/s. Do these measurements match each other within their experimental uncertainty? (explain your reasoning)