A fly-wheel of mass 25 kg has a radius of 0.2 m. It is making 240 rpm . What is the torque necessary to bring to rest in 20 s?

Question

A fly-wheel of mass 25 kg has a radius of 0.2 m. It is making 240 rpm . What is the torque necessary to bring to rest in 20 s? (A) 2 π Nm (B) 0.4 π Nm (C) (2/π) Nm (D) 4 π Nm

Tardigrade Admin · Accepted Answer

α=(2 π n/t) =(2 π × (240/60)/20) =(2 π × 4/20) α =(2 π/5) Torque, τ =I α τ =M R2 α =25 ×(0.04) × (2 π/5) =0.4 π Nm

Q. A fly-wheel of mass $25 k g$ has a radius of $0.2 m$ . It is making $240 r p m .$ What is the torque necessary to bring to rest in $20 s$ ?

$2 π N m$

$0.4 π N m$

$\frac{2}{π} N m$

$4 π N m$

$α = \frac{2 πn}{t} = \frac{2 π \times \frac{240}{60}}{20}$
$= \frac{2 π \times 4}{20}$
$α = \frac{2 π}{5}$
Torque, $τ = I α$
$τ = M R^{2} α$
$= 25 \times (0.04) \times \frac{2 π}{5}$
$= 0.4 π N m$

Q. A fly-wheel of mass 25kg has a radius of 0.2m. It is making 240rpm. What is the torque necessary to bring to rest in 20s?

2πNm

0.4πNm

π2​Nm

4πNm