A simple pendulum is known to have a period, T = 1.55 s. Student A uses their smartphone stopwatch app to measure the total time for 5 oscillations and divides that by 5 to report an average period of T = 1.25 s. Student B uses the same technique but goes old school and whips out his grandpa’s analog stopwatch to come up with an average of T = 1.5 s. What is the most probable source of error that explains the different results?

a

explanation:

no diagram was provided, but i'm guessing it's the one i've attached to my answer.

here, a mechanical force turns the rod.   this generates an electric current in the coil, which powers the bulb.

blue light is scattered in different directions by the tiny molecules of air. blue is scattered more than other colours because it has a shorter distance to travel which results in smaller waves. this is why we see a blue sky most of the time.