Lab Session # 1
Objective:
To determine the Moment of Inertia of a Flywheel. ]
Apparatus:
Flywheel Apparatus, Meter Rod, Stop Watch, Hanger, Different Weights
Schematic Diagram:
Theory:
Flywheel:
Flywheel is a rotating mechanical device that is used to store the rotational energy. Flywheel
has a significant moment of inertia and thus resists the change in rotational speed. The amount of
energy stored in flywheel is proportional to the square of its speed. Energy is transferred to a flywheel
by applying the torque to it, thereby increasing its rotational speed, and hence it stored energy.
Moment of Inertia:
` Moment of inertia is the mass property of a rigid body that determines the torque needed for a
desired angular acceleration about an axis of rotation. Moment of inertia depends upon the shape of
the body may be different about different axis of rotation.
Mass Moment of Inertia:
The mass moment of inertia is the one measure of distribution of the mass of an objective
relative to a given axis. The mass moment of inertia is denoted by “Io” and is given for a single
particle of mass “m” as
Io=r2m
Where 0-0 is the axis around which one is evaluating the mass moment of inertia and “r” is
the perpendicular distance between the mass and axis. The mass moment of inertia has the unit of
Kgm2.
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Difference between Flywheel and Governor Apparatus:
Flywheel Governors Apparatus:
A fly wheel is an energy storing device A governor is a device used to regulate
that is used to store energy in machines. It mean speed of an engine when there are
absorbs the mechanical energy when the variations in load.
supply of energy is more by increasing Governor is a rotating body which has in
angular velocity and vice versa. its side. It keeps on rotating when a vehicle
It is a device that stores the rotational as it is connecting to the power.
energy during access energy and supplies It is device used to control the load
energy when it is required. variation by adjusting the flow of fuel.
Flywheel is more economical than
governor as it reduces running expenses of
the prime mover whereas this is a chance
of more consumption of fluid.
Applications:
It absorbs braking energy.
It is used in punching machines.
It delivers accelerating energy for an automobile.
It acts as energy-smoothing devices for electric utilities as well as solar and wind-power
generating facilities.
Flywheels are used in electric railways for regenerative braking by feeding braking energy
back into power lines.
Procedure:
In this experiment, firstly I attached a hanger with fly wheel with the help of rope.
Rotated the fly wheel so that the thread rolled on its axis. The number of rolls of thread around
the axis are the no. of revolutions for the fly wheel. After selecting no. of revolutions, we have to
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measure the distance from the bottom of weight hanger to the ground surface. After measuring
distance, we have to apply weights on the hanger slowly holding flywheel with one hand.
After applying weights, leave the flywheel and note the time of falling of hanger on the ground
with the help of stopwatch when just hit the ground. First, I apply 3N weight on the hanger, and I
make 13 revolutions of thread around the axis of flywheel. The height of hanger at this time wass
0.87cm. I left the flywheel to move and it hit the ground in 38 sec. Repeated the experiment
three times for same height and weight and three times for different heights and weights.
Observations & Calculations:
Wheel weight W=31.07 kg, Wheel radius R=0.170 m, Spindle radius r=0.012 m
Time for Falling & Angular
Moment of Inertia
“N” Revolutions Velocity
I
Load Height T ω
Sr No. of “N” (Nm2)
P H (sec) (rad/sec)
.# Revolutions
(N) (m)
ω=2πNN/ I=Pr2T2avg/
T 1 T 2 T T
3 avg I=2PH/ ω2
Tavg 2H
1 3 0.87 13 38 38.56 41.13 39.23 2.08 0.384 1.21
2 3 1.20 19 45 40.96 36.6 40.85 2.92 0.285 0.91
3 4 1.07 16 36.5 36.90 36.33 36.68 2.74 0.360 1.140
Comments:
Bearings of flywheel should be greased for smooth rotations of flywheel
There should be proper way to measure height of hanger from ground for this we can
place a measuring scale on wall where the apparatus is placed.
However, with the help of this apparatus I got the required results which shows inverse
relation between moment of inertia and angular velocity.
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