A student uses a simple pendulumof exactly 1m length to determine g, the acceleration due to gravity. He uses a stop watch with the least count of 1 sec for this and records 40 secondsfor 20 oscillations. For this observation, which of the following statement(s) is (are) true ?

A

Error $$\triangle T$$ in measuring T, the time period, is 0.05 seconds

B

Error $$\triangle T$$ in measuring T, the time period, is 1 second

C

Percentage error in the determination of g is 5%

D

Percentage error in the determination of g is 2.5%