Experiment Name: To determine the value of g acceleration due to gravity by means of compound pendulum.

Theory: Compound pendulum is a rigid body of any shape free to turn about a horizontal axis. When the body oscillates about a hole from one end or the corresponding hole from the other end, then the time periods are the same. Then the time period of oscillation T is found from the following

relation, T=2 We get, g=4 2 2

By finding L graphically, and determining the value of the period T, the acceleration due to gravity g at the place of the experiment can be determined.

Apparatus: A set of simple pendulum.

Procedure: 1) Find out the centre of gravity G of the bar.

2) Insert a metal wedge in the first hole in the bar towards A and place the wedge on the

support S1S2 so that the bar can turn round S.

3) Set the bar to oscillate taking care to see that the amplitude of oscillations is not more than 50. Note the time for 50 oscillations.

4) Measure the length from the end A of the bar to the top of the first hole i.e., up to the

point of suspension of the pendulum.

5) In the same way, suspend the bar at holes 2, 3, and each time note times for 50 oscillations. Also measure distances from the end A for each hole.

6) When the middle of the bar is passed, it will turn round so that the end B is now on

the top. But continue measuring the distances from the point of suspension to the end A.

7) Now calculate the time period T from the time recorded for 50 oscillations.

8) On a nice and large graph paper, plot a curve with length as abscissa and period T as ordinate with the origin at the middle of the paper along the abscissa.

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Experimental Data:

TABLE

Position Hole No.

Distance from end A

(cm)

Time for 20 Oscillations

(sec)

Time Period

(sec)

End A 1 10 30.99 1.55 2 20 30.40 1.52 3 30 31.41 1.57 4 40 36.86 1.84

End B 1 90 31.16 1.55 2 80 30.19 1.51 3 70 31.42 1.57 4 60 38.3 1.91

Calculations: From graph, AC= 59 cm BD= 59 cm Mean length, = = 59 cm Corresponding time period,T = 1.55 sec Acceleration due to gravity, g=4 2 2 = 969.5 cm sec-2 = 9.695 meter sec-2 Result: Acceleration due to gravity, g= 9.695 meter sec-2 Error := . .

. 100 = 1.07 %

Discussions: 1.in this experiment , we have to face some problem . 2.we used stop watch in this experiment carefully.Stopwatch should be started in a just time. 3. By the way we must have to take the movement of steel bar carefully . 4.Get every distance from point to another point was equal by verifies.