Experiment # 02
To find the moment of inertia of flywheel
By falling weight method
Objective#
To calculate the moment of inertia of flywheel.
Apparatus used#
Fly wheel apparatus
Stop watch
Rope
Scale
Theoretical Background#
Fly wheel#
A heavy revolving wheel in a machine which is used
to increase the machine’s momentum and thereby
provide greater stability or a reserve of available
power.

Scale#
Scale is used for measuring the change in length and
also the length of inclined plane
Stop watch#
Stop watch is used to note a time.
Moment of inertia#
“The resistance to rotational or circular motion is
called
moment of inertia”
It depends on mass and radius of body. It is
represented by “I”.
Let “L” be the length of the inclined plane and “m” be
the mass of wheel.
s = vav t
let vi = 0
s = (vi + vf)t/2
s = (vf)t/2
vf = 2s/t
Potential energy at height “h” is
P.E = mgh
Kinetic energy, K.E = (mv2
)/2
Rotational K.E = K.Erot = (Iw2
)/2
According to law of conservation of energy
P.E = K.E + K.Erot
mgh = (mv2
)/2 + (Iw2
)/2
2mgh = mv2
+ Iw2
I = (2mgh – mv2
)/w2
Where
w = v/r (r is radius & v is velocity of wheel)

Experimental Procedure#
First of all we adjust the apparatus, at a height (h) we
adjust the hanger at a desired height.
After that a weight of certain value is put on it and
allowed it to move down the point at which it touches
the earth will be noted with the help of stop watch.
The values which we put into the formulae of
moment off inertia gives desired value.
This procedure is repeated for various loads and
heights.
Observation and calculations#
R=0.5 inch
R=0.5/12=0.042 f
Table
S. No m r H t V=2H/t ω=V/r I
1. 0.318 lb. 0.041 ft. 3.583 ft. 8 sec 0.895 ft/sec2
21.48 rad/sec 0.258 lb.ft2
2. 0.131 lb. 0.041 ft. 3.437 ft. 20 sec 0.343 ft/sec2
8.232 rad/sec 0.261 lb.ft2
3. 0.069 lb. 0.041 ft. 2.333 ft. 22 sec 0.212 ft/sec2
5.088 rad/sec 0.254 lb.ft2
4. 0.1 lb. 0.041 ft. 3.333 ft. 17 sec 0.392 ft/sec2
9.408 rad/sec 0.257 lb.ft2
5. 0.194 lb. 0.041 ft. 3.541 ft. 11.5 sec 0.615 ft/sec2
14.76 rad/sec 0.267 lb.ft2
6. 0.16 lb. 0.041 ft. 3.667 ft. 14 sec 0.523 ft/sec2
12.552 rad/sec 0.2601 lb.ft2
7. 0.22 lb. 0.041 ft. 4.166 ft. 12.5 sec 0.666 ft/sec2
15.984 rad/sec 0.249 lb.ft2
8. 0.1 lb. 0.041 ft. 3.041 ft. 15.5 sec 0.392 ft/sec2
9.408 rad/sec 0.269 lb.ft2

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