An energy of 484 J is spent in increasing the speed of a flywheel from...
From work - energy theorem
W = Δk (change in Kinetic Energy)
In rotation,

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An energy of 484 J is spent in increasing the speed of a flywheel from...
Given:
- Energy spent in increasing the speed of the flywheel = 484 J
- Initial speed of the flywheel = 60 rpm
- Final speed of the flywheel = 360 rpm
To Find:
Moment of inertia of the flywheel
Formula:
The energy spent in increasing the speed of a rotating body can be given by the formula:
E = (1/2) * I * (ω^2 - ω0^2)
Where:
E = Energy spent (in Joules)
I = Moment of inertia (in kg-m^2)
ω = Final angular velocity (in rad/s)
ω0 = Initial angular velocity (in rad/s)
Calculation:
Given that the initial speed of the flywheel is 60 rpm, we can convert it to radians per second using the formula:
ω0 = (2π/60) * 60 = 2π rad/s
Similarly, the final speed of the flywheel is 360 rpm, which can be converted to radians per second:
ω = (2π/60) * 360 = 12π rad/s
Substituting the values into the formula for energy spent:
484 = (1/2) * I * ((12π)^2 - (2π)^2)
Simplifying the equation:
484 = (1/2) * I * (144π^2 - 4π^2)
484 = (1/2) * I * (140π^2)
Now, dividing both sides of the equation by (1/2) * (140π^2):
I = 484 / (1/2) * (140π^2)
Simplifying further:
I = 484 / (70π^2)
I = 2/π^2
Approximating the value of π to 3.14:
I ≈ 2/(3.14)^2
I ≈ 2/9.8596
I ≈ 0.202 kg-m^2
Therefore, the moment of inertia of the flywheel is approximately 0.202 kg-m^2.
Conclusion:
The moment of inertia of the flywheel is approximately 0.202 kg-m^2, which matches with option 'B' (0.7 kg-m^2).