# 2 - Error Analysis Questions Answers

A resistor of 10kΩ having tolerance 10 % is connected in series with another resistor of 20 kΩ having tolerance 20 %. The tolerance of the combination will be approximately.

Joshi sir comment

resultant = (10±1)+(20±4) = 30±5

so tolerance = 5*100/30 = 50/3 = 16.67 %

the time period of oscillatn of a simple pendulum is 2π (l/g)1/2.  l is about 10cm & is known to 1mm accuracy. the time period of oscillatn is about 0.5s . time of 100 oscillatn with a wrist watch of 1s revolutn . what is the accuracy in determinatn of g?

ans 5%

Solution by Joshi sir

T = 2π (l/g)1/2

so g α  l/T2

so % error in g = % error in l + 2 % error in T

=  0.1*100/10  + 2* 1*100/50 = 1+4 = 5

here you shoult remember that if you count 100 osccilations then time will be counted for 100 osccilation.