The diameter of a flywheel is 1 m . It has a mass of 20 kg . It is rotating about its axis with a speed of 120 rotations in one minute. Its angular momentum in kg m 2 s-1 is

Question

The diameter of a flywheel is 1 m . It has a mass of 20 kg . It is rotating about its axis with a speed of 120 rotations in one minute. Its angular momentum in kg m 2 s-1 is (A) 13.4 (B) 31.4 (C) 41.4 (D) 43.4

Tardigrade Admin · Accepted Answer

Here, d=1 m, v=120 rpm , M=20 Kg r=(d/2)=(1/2) m=0.5 m ω=2 π v=(2 π × 120/60)=4 π rad s-1 ∴ L=I ω=(M r2/2) ω=(20 ×(0.5)2 × 4 π/2) =10 × 0.25 × 4 × 3.14=31.4 kg m2 s-1

Q. The diameter of a flywheel is $1 m$ . It has a mass of $20 k g$ . It is rotating about its axis with a speed of $120$ rotations in one minute. Its angular momentum in $k g m^{2} s^{- 1}$ is

13.4

31.4

41.4

43.4

Here, $d = 1 m, v = 120 r p m, M = 20 K g$
$r = \frac{d}{2} = \frac{1}{2} m = 0.5 m$
$ω = 2 π v = \frac{2 π \times 120}{60} = 4 π r a d s^{- 1}$
$∴ L = I ω = \frac{M r ^{2}}{2} ω = \frac{20 \times ( 0.5 ) ^{2} \times 4 π}{2}$
$= 10 \times 0.25 \times 4 \times 3.14 = 31.4 k g m^{2} s^{- 1}$

Q. The diameter of a flywheel is 1m . It has a mass of 20kg . It is rotating about its axis with a speed of 120 rotations in one minute. Its angular momentum in kgm2s−1 is