Question

Time for $20$ oscillations of a pendulum is measured as $t_1=39.6s,t_2=39.9s$ and $t_3=39.5s$. What is the accuracy of the measurement?

• A. $\pm .2sec$
• B. $\pm 0.005$
• C. $\pm .1$
• D. $0$

Answer 1

The correct option is B $\pm 0.005$

According to the problem time for $20$ oscillations of a pendulum

$t_1=39.6s$, $t_2=39.9s$, $t_3=39.5s$

It is quite obvious from these observations that the least count by the water is $0.1s$. As measurements have only one decimal place. Precision in measurement $=$ least count of measuring instrument $=0.1s$

Precision in $20$ oscillations $=0.1$

Therefore, Precision in $1$ oscillation $=\frac{0.1}{20}=0.005$.