Apparatus:
Flywheel, two weights 300 gm and 200 gm, cotton string, stop-watch, metre rod and vernier caliper.
Observation:
Vernier constant of the vernier callipers =………..cm
Diameter of the axle 1 st position (d 1) =………. cm
Diameter of the axle 2nd position (d2) =……..cm
Mean diameter or the axle d = (d1 + d2) / 2 =……….cm
Radius of the axle (d2 = d / 2) =………..cm
Procedure:
Make a small loop at one end of the string so that it may be put round the peg. P, on the axle of the flywheel. Tie a weight. Mg, at its other end. Rotate the wheel with the hand and wrap the string round the axle.When the weight is at A (a little below the rim) put a set-square under it and make a mark A on the wall (or on the side of the table). Now let the weight descend, the string will get unwrapped as the wheel turns. The length of the string is so adjusted that when the weight rests on a wooden block W, resting on the ground, the string is just tight and is on the point of slipping off the peg P. A mark B’ is made at the level of E on the wall. Thus we know that when the weight will be let fall from A. it will fall through a height = A’B’ before getting detached from the peg. Also count the rotations, m, made by the wheel while the weight falls from A to B. This is facilitated by observing the mark 11. made on the rim, as the wheel rotates.
The thread is wound up again, so that the weight is at A, the block of wood is removed and the weight allowed to fall. As soon as the weight goes off the peg, start a stop-watch, Count the number ‘n’ of rotations made by the wheel before coming to rest (starting from the moment the weight was detached from P) and note the time taken for this purpose.
Measure the diameter of the axle in two mutually perpendicular directions and determine the mean radius.
First put mass of 300 gms and then add mass of 200 gms in the hanger to repeat the experiment.
Calculations:
The formula for the determination of moment of inertia of a flywheel is given by.
Moment of inertia =
Result:
Moment of inertia of the flywheel about its axle = 1 =……….gm-cm²
Precautions:
1. In determination of height, h, the positions of the bottom of the weight are to be marked on the wall in the two cases i.e. when the weight is at A and when at B.
2. The diameter of the axle should be determined in two mutually perpendicular directions.
3. While adjusting the length of string, see that when the weight is resting on the block ‘W, the string is just tight and is on the point of slipping off the peg.
4. The timing and counting of rotations should commence from the instant the weight goes off the peg.
5. If the wheel makes less than 100 rotations before stopping, there is a considerable friction and the axle should be oiled.
VIVA VOCE
Q.1. what is meant by moment of inertia?
Ans. The sluggishness of the rotating body to change its state of rotation or of rest is called as moment of inertia.
Q.2. what is meant by radius of gyration?
Ans. The radius of gyration of a body with respect to any axis is the radius of thin ring which is centred on the axis and which has the same mass and moment of inertia as that of the given body.
Q.3. Does the moment of inertia depends on the axis of rotation?
Ans. Yes moment of inertia depends on the axis of rotation.
Q.4. what is meant by inertia?
Ans. Inertia is that property due to which a body keeps on doing whatever it is doing unless
Force to change its state. Its depend on the mass of the body.
Q.5. Where does the center of gravity of flywheel is lie?
Ans.The center of gravity of wheel lies on the axis of rotation.
Q.6. Give the units of moment of inertia?
Ans. Moment of inertia is expressed in gm cm² or kg/m².
