A fly wheel is a uniform disc of mass 72 kg and radius 50 cm . When it is rotating at the rate of 70 rpm, its kinetic energy is

Question

A fly wheel is a uniform disc of mass 72 kg and radius 50 cm . When it is rotating at the rate of 70 rpm, its kinetic energy is (A) 142 J (B) 242 J (C) 342 J (D) 300 J

Tardigrade Admin · Accepted Answer

Kinetic energy of flywheel, K =(1/2) I ω2=(1/2) × (1/2) M R2 ω2=(1/4) M R2 ω2 =(1/4) × 72((50/100))2((2 π × 70/60))2=241.5 J ∼ 242 J .

Q. A fly wheel is a uniform disc of mass $72 k g$ and radius $50 c m .$ When it is rotating at the rate of $70 r p m$ , its kinetic energy is

142 J

242 J

342 J

300 J

Kinetic energy of flywheel,
$K = \frac{1}{2} I ω^{2} = \frac{1}{2} \times \frac{1}{2} M R^{2} ω^{2} = \frac{1}{4} M R^{2} ω^{2}$
$= \frac{1}{4} \times 72 (\frac{50}{100})^{2} (\frac{2 π \times 70}{60})^{2} = 241.5 J \sim 242 J$ .

Q. A fly wheel is a uniform disc of mass 72kg and radius 50cm. When it is rotating at the rate of 70rpm, its kinetic energy is