Moment Of Inertia Of Flywheel 3a633q

Moment of Inertia of Flywheel Aim: To determine the moment of inertia of a flywheel.

Apparatus: Fly wheel, weight hanger, slotted weights, stop watch, metre scale.

Theory: The flywheel consists of a heavy circular disc/massive wheel fitted with a strong axle projecting on either side.The axle is mounted on ball bearings on two fixed s. There is a small peg on the axle. One end of a cord is loosely looped around the peg and its other end carries the weight-hanger. Let "m" be the mass of the weight hanger and hanging rings (weight assembly).When the mass "m" descends through a height "h", the loss in potential energy is

The resulting gain of kinetic energy in the rotating flywheel assembly (flywheel and axle) is

Where I -moment of inertia of the flywheel assembly ω-angular velocity at the instant the weight assembly touches the ground. The gain of kinetic energy in the descending weight assembly is,

Where v is the velocity at the instant the weight assembly touches the ground. The work done in overcoming the friction of the bearings ing the flywheel assembly is

Where n - number of times the cord is wrapped around the axle Wf - work done to overcome the frictional torque in rotating the flywheel assembly completely once Therefore from the law of conservation of energy we get

On substituting the values we get

Now the kinetic energy of the flywheel assembly is expended in rotating N times against the same frictional torque. Therefore

and If r is the radius of the axle, then velocity v of the weight assembly is related to r by the equation

Substituting the values of v and Wf we get:

Now solving the above equation for I

Where, I = Moment of inertia of the flywheel assembly N = Number of rotation of the flywheel before it stopped m = mass of the rings n = Number of windings of the string on the axle g = Acceleration due to gravity of the environment. h = Height of the weight assembly from the ground. r = Radius of the axle. Now we begin to count the number of rotations, N until the flywheel stops and also note the duration of time t for N rotation. Therefore we can calculate the average angular velocity

in

radians per second.

Since we are assuming that the torsional friction Wf is constant over time and angular velocity is simply twice the average angular velocity

Applications: Flywheels can be used to store energy and used to produce very high electric power pulses for experiments, where drawing the power from the public electric network would produce unacceptable spikes. A small motor can accelerate the flywheel between the pulses. The phenomenon of precession has to be considered when using flywheels in moving vehicles. However in one modern application, a momentum wheel is a type of flywheel useful in satellite pointing operations, in which the flywheels are used to point the satellite's instruments in the correct directions without the use of thrusters rockets.

Flywheels are used in punching machines and riveting machines. For internal combustion engine applications, the flywheel is a heavy wheel mounted on the crankshaft. The main function of a flywheel is to maintain a near constant angular velocity of the crankshaft.

Procedure 1. The length of the cord is carefully adjusted, so that when the weight-hanger just touches the ground,the loop slips off the peg. 2. A suitable weight is placed in the weight hanger 3. A chalk mark is made on the rim so that it is against the pointer when the weight hanger just touches the ground. 4. The other end of the cord is loosely looped around the peg keeping the weight hanger just touching the ground. 5. The flywheel is given a suitable number (n) of rotation so that the cord is wound round the axle without overlapping. 6. The height (h) of the weight hanger from the ground is measured. 7. The flywheel is released. 8. The weight hanger descends and the flywheel rotates. 9. The cord slips off from the peg when the weight hanger just touches the ground.By this time the flywheel would have made n rotations. 10. A stop clock is started just when the weight hanger touches the ground. 11. The time taken by the flywheel to come to a stop is determined as t seconds. 12. The number of rotations (N) made by the flywheel during this interval is counted. 13. The experiment is repeated by changing the value of n and m. 14. From

these

values

the

moment

of

inertia

Observations

Mean value of moment of inertia,I =.........kgm2

Result Moment of inertia of the fly wheel =.........kgm2

of

the

flywheel

is

calculated

using

equation