(a) Precision is given by the least count of the instrument.
For 20 oscillations, precision = 0.1 s
For 1 oscillation, precision = 0.005 s.
Average time for 20 oscillations
\(t=\frac{39.6+39.9+39.5}{3}s=39.7sec\)
Absolute errors,
∆t1 = t − t1
= 39.7 – 39.6
= 0.1 s.
∆t2 = t − t2
= 39.7 – 39.9 = −0.2s
∆t3 = t − t3
= 39.7 – 39.5
= 0.2s
Mean absolute error,
\(=\frac{|Δt_1|+|Δt_2|+|Δt_3|}{3}\)
\(=\frac{0.1+0.2+0.3}{3}\)=\(\frac{0.5}{3}\)
= 0.17
≈ ±0.2s.