Question Details

A flywheel is attached to an engine to keep its rotational speed between 100 rad/s and 110 rad/s. If the energy fluctuation in the flywheel between these two speeds is 1.05 kJ then the moment of inertia of the flywheel is _______ kg.m² (round off to 2 decimal places).

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Correct Answer :

Correct answer is : 1

ω1 = 110 rad/sec, ω2 = 100 rad/sec, ΔKE = 1.05 kJ = 1050 J

1050 =  1 2 × I f × ( 110 2 100 2 )

I f = 1 k g . m 2

Solution :

The correct answer is 1.

Understanding the Concept of Flywheel Energy Fluctuation:
A flywheel is a mechanical device specifically designed to store rotational kinetic energy. The kinetic energy (KE) of a rotating body is given by the formula:
KE=12Iω2
where:
- I is the moment of inertia of the flywheel (in kg.m²),
- ω is the angular velocity (in rad/s).

When the rotational speed fluctuates between a minimum speed (ω2) and a maximum speed (ω1), the energy stored in the flywheel fluctuates as well. The maximum fluctuation of energy (ΔKE) is the difference between the kinetic energy at the maximum speed and the kinetic energy at the minimum speed:
ΔKE=KEmax-KEmin=12Iω12-1 Harris">2Iω22
Factoring out the common terms, we get:
ΔKE=12I(ω12-ω22)

Step-by-Step Derivation and Calculation:
Given the following data:
- Maximum angular speed, ω1=110 rad/s
- Minimum angular speed, ω2=100 rad/s
- Energy fluctuation, ΔKE=1.05 kJ=1050 J

Substitute these values into the energy fluctuation formula:
1050=12×I×(1102-1002)

Calculate the squares of the angular speeds:
1102=12100
1002=10000

Find the difference between the squares:
1102-1002=12100-10000=2100

Now, substitute this back into the equation:
1050=12×I×2100
Simplify the equation:
1050=1050×I
Solve for the moment of inertia (I):
I=10501050=1 kg.m2

Thus, the moment of inertia of the flywheel is 1 kg.m².

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