Question

The least count of a stop-watch is $\left(1/5\right)s$. The time of $20$ oscillations of a pendulum is measured to be $25s$. What is the maximum percentage error in this measurement ?

• A. $8\%$
• B. $1\%$
• C. $4\%$
• D. $16\%$

Answer 1

Answer: (C)

$4\%$

Number of oscillation $=20$

Total time taken for $20$ oscillation $=25sec$

Time period $=25/20=1.25sec$

Least count of watch $=0.2sec$

The measurement of time period $1.25$ the measuring watch can measure upto $0.2s$ thus the watch can measure $1.2s$ but the uncertainity remains in the $0.05s$.

$1.25s=1.2+0.05$

Thus, error $=0.05sec$

Percentage error $=\left(0.05/1.25\right)\times 100=4\%$