A stopwatch has least count 1/5 s. Time for 20 oscillations of a pendulum is measured as 25 s. Find maximum percentage error in the period expressed in multiples of 0.4%.
Physics · Mixed Chapter
JEE Main Practice

Question

A stopwatch has least count 1/5 s. Time for 20 oscillations of a pendulum is measured as 25 s. Find maximum percentage error in the period expressed in multiples of 0.4%.

G1 Physics · Accepted Answer

Step 1: Period T=t/20, and 20 is an exact counted integer. Step 2: Absolute timing error ≤0.2 s, giving relative period error=0.2/25=0.008. Step 3: Percentage period error=0.8%. Step 4: Since 0.8%=2×0.4%, required multiple=2.