slader A uniform cylindrical grinding wheel of mass 50.0 kg and diameter 1.0 m is turned on by an electric motor. The friction in the bearings is negligible. What torque must be applied to the wheel to bring it from rest to 120 rev/min in 20 revolutions?

Respuesta :

Answer:

The value of torque on the rod is = 3.94 N - m

Explanation:

mass = 50 kg

Radius = 0.5 m

Moment of inertia ( I ) = [tex]\frac{MR^{2} }{2}[/tex]

[tex]I = 50 \frac{0.5^{2} }{2}[/tex]

I = 6.25 kg- [tex]m^{2}[/tex]

Angular velocity [tex]\omega[/tex] = 120 [tex]\frac{Rev}{min}[/tex] = 12.6 [tex]\frac{rad}{sec}[/tex]

Δ[tex]\theta[/tex] = No. of rev × 2[tex]\pi[/tex]

Δ[tex]\theta[/tex] = 20 × 2[tex]\pi[/tex]

Δ[tex]\theta[/tex] = 126 rad

From work energy theorem  

Work done is equal to change in kinetic energy.

[tex]W_{AB} = K_{B} - K_{A}[/tex] -------- (1)

Where A & B represents the initial & final states.

Since [tex]K_{A}[/tex] = 0

[tex]W_{AB} = K_{B}[/tex]

[tex]W_{AB} = \frac{1}{2} I \omega^{2}[/tex]

[tex]W_{AB} = \frac{1}{2} 6.25 (12.6)^{2}[/tex]

[tex]W_{AB} =[/tex] 496 J

We know that

[tex]W_{AB} =[/tex] T Δ[tex]\theta[/tex]

Where [tex]W_{AB} =[/tex] work done

T = torque applied on the rod

Δ[tex]\theta[/tex] = Angular displacement of the rod.

496 = T × 126

T = 3.94 N - m

Therefore the value of torque on the rod is = 3.94 N - m