Question

4. The least count of a stop watch is second. The
time of 20 oscillations of a pendulum is measured
to be 25 seconds. The maximum percentage error
in the measurement of time will be
(1) 0.1%
(2) 0.8%
(3) 1.8%
(4) 8%
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Answer 1

Answer:

Number of oscillations n=20

Time taken =25 s

∴ Time period of oscillation T=

20

25

=1.25 s

Given :

Error in time for 20 oscillations, ΔT=0.2 s

Hence error in time for 1 oscilations, ΔT

′

=

n

0.2

= s

∴ Percentage error =

T

ΔT

×100=

20×1.25

0.2×800

= 0.8 sec ans