The length of a simple pendulum which makes 20 oscillations in 36 seconds (at place where the acceleration due to gravity 9.75 m/s2 ) is

Question

The length of a simple pendulum which makes 20 oscillations in 36 seconds (at place where the acceleration due to gravity 9.75 m/s2 ) is (A) 70 cm (B) 80 cm (C) 90 cm (D) 60 cm

Tardigrade Admin · Accepted Answer

Given g = 9.75 m/s2 T= (36/20) = 1.8 sec Using, L = (gT2/4 π2) = (9.75 × (1.8)2/4 × 10) : :: : : ( ∵ π2 ≈ 10) = 0.79 m = 79 cm ≈ 80 cm

Q. The length of a simple pendulum which makes 20 oscillations in 36 seconds (at place where the acceleration due to gravity $9.75 m / s^{2}$ ) is

70 cm

80 cm

90 cm

60 cm

Given $g = 9.75 m / s^{2}$
$T = \frac{36}{20} = 1.8 sec$
Using, $L = \frac{g T ^{2}}{4 π ^{2}} = \frac{9.75 \times ( 1.8 ) ^{2}}{4 \times 10} (∵ π^{2} \approx 10)$
= 0.79 m = 79 cm $\approx$ 80 cm

Q. The length of a simple pendulum which makes 20 oscillations in 36 seconds (at place where the acceleration due to gravity 9.75m/s2 ) is