The gravitational acceleration,$g$ can be determined by using a pendulum. If a pendulum of length $l$ has a period of $T$ s. A 2m pendulum is timed to take 57 s for 20 swings.
A)calculate the value of $g$ from the data. B) find an expression for the approximate error in $g$ for an error of $\delta t$ in the timing of $20$ swings. C)calculate the possible error in $g$ if the timing was made to the nearest second.
I solved question a. But I've no idea for the question b and c. Can anyone explain it to me? Thanks