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Experiment 3 : DETERMINATION OF

GRAVITATIONAL ACCELERATION AND COIL SPRING

Lecturer’s Name : Prof. Madya Dr Shahrin Bin Ibrahim

GROUP MEMBER MATRIC NO

NUR SYAFIKA BINTI ZAMRI 156747

NUR ASHIKIN BINTI ZOLKEFLI 157432

HIDAYAH BINTI KHAMISAN 157463

NURLINA BINTI RIDWAN 159067

HAFSAHBINTI MOHD CHABAR 157148

SELVAGANESH PRASAD 156570

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INTRODUCTION

In this part of the experiment, you will be experimenting with as simple pendulum as

illustrated in Figure 1. The pendulum consists of a plumb bob with a heighth 

from thefloor of the lab attached with a string of l. The other end of string is attached or tied to

the ceiling of height H from the floor.

For a simple pendulum, if the oscillation is SMALL, then the period T of a TO AND FRO

oscillation is given an equation:-

T = 2 П    ………. (1) 

Where g is the gravitational acceleration.

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METHODOLOGY

1. The height, h of the plum bob was measured from the floor.

2. The plum bob was set into small oscillation and the time taken for a 50 complete

oscillation to take place were recorded.

3. Step (1) and (2) was repeated for another 6 different height as shown in the tablebelow for both first floor and ground floor situation.

4. Results of T and h had been tabulated.

RESULT AND DISCUSSION

Result

Ground Floor First Floor 

Length

(Centimeter)

Time

Requiredfor 50

Oscillator (second)

Length

(Centimeter)

Time

Requiredfor 50

Oscillator (second)

274.8 2.43 260.5 2.41

264.8 2.40 250.5 2.35

254.8 2.38 240.5 2.34

244.8 2.35 230.5 2.32

234.8 2.33 220.5 2.30

224.8 2.30 210.5 2.26

214.8 2.27 200.5 2.23

*Center of Mass of the Cone =¼ from the basement of the cone

*50 from the cone line = x= (tan 50 / 274.8 cm) = 24 cm

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1622.7

1525.2

1443.3

1351.9

1274.71189.2

1106.8

0

200

400

600

800

1000

1200

1400

1600

1800

0 10000 20000 30000 40000 50000 60000 70000 80000

   L   T   2 

L2

lT2 against l2 for first floor 

Gradient,k =31.4136

Gradient,k =29.4118

1622.7

1525.2

1443.3

1351.9

1274.71189.2

1106.8

0

200

400

600

800

1000

1200

1400

1600

1800

0 10000 20000 30000 40000 50000 60000 70000 80000

   L   T   2 

L2

lT2 against l2 for ground floor 

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According to Newman and Searle (1951, 22-23), the period, P, of a compound

pendulum is

T = 2 π[( k 2

+ l 2 )/lg )

1/2 ] , (1)

where g is the acceleration of gravity and k is the radius of gyrationBy differentiation of equation 1, it is easily shown that the minimum value of T is

T min= 2π  2k / g .

,where we obtain

T min= 1.54 ± 0.01 s; hence, 

k = 29.5 ± 0.5 cm,

where we have used the value of

 g = 981 cm/  for the acceleration of gravity

thus from graph 1 ,the k=31.4136 which correspond to 1044.1 cm/ and from graph 2k=29.4118 which gives 978.0 cm/. The value of k agrees well with the calculatedresult, and  g is close to the accepted value of 981 cm/. Graph 2 shows that thecalculated values of P agree best with the experimental values for P in excess of T min.This fact explains why the straight line graph gives a value of k that agrees well with thecalculated value . The experimental value of g was found to be 9.78 m/ which is 0.2%below the theoretical value of 9.80 m/ . Since the percent error in g is below thepercent uncertainty in the experiment, the diff erence between the theoretical andexperimental values can be attributed to measurement uncertainty. Therefore, ourexperiment supports the theoretical result that the acceleration due to gravity is 9.80m/s2..