Question

The least count of a stop watch is $1/5$ sec. The time of $20$ oscillations of a pendulum is measured to be $25$ sec. The minimum percentage error in the measurement of time will be:

• A. $0.1\%$
• B. $0.8\%$
• C. $1.8\%$
• D. $8\%$

Answer 1

Answer: (B)

$0.8\%$

$\Delta T=\frac{0.2}{20}$
$T=\frac{25}{20}=1.25$
$\frac{\Delta T}{T}=\frac{\frac{0.2}{20}}{1.25}\times 100=0.8\%$