• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Investigating the Oscillations of an Obstructed Pendulum

Extracts from this document...


Aroma Kazmi

                Year 12


Oscillations of an Obstructed Pendulum


To investigate how – in an obstructed pendulum – varying the distance from the top of the pendulum to the obstruction affects the time period of one horizontal oscillation, and to use this information to verify the relationship shown below. After verifying the relationship, the value of ‘g’ must be derived from the graph.

The mass, physical shape and physical properties will be kept constant. The positioning of the stand, the orientation of the obstruction, and the angle of displacement will be kept the same. In addition to this, the mass and physical properties will be kept the same. The room conditions will be minimized, and external wind will be kept to a minimum.

The equation that must be verified is:

t=-π2gdt+2π lg


g = gravitational acceleration (ms-1)

d = distance from top of pendulum to obstruction (m)

t = time taken for one oscillation (s)


Independent Variable:

The distance from the top of the pendulum to the obstruction (40cm, 45cm, 50cm, 55cm, 60cm, 65cm, 70cm).

Dependent Variable:

The time period of one oscillation

Control Variables:         

  • Mass and properties of the bob being used
  • Angle of displacement (10°)
  • Mass and physical properties of the string being used
  • Positioning and location of the stand
  • The orientation of the obstruction
  • Room conditions


  • 1 stand to which the spring, the bob, and the obstruction will be attached
  • 1 bob of mass 100g
  • 1 string
  • 1 wooden rod of approximately 15cm length (obstruction)
  • 1 stopwatch
  • 1 metre ruler

Risk Assessment:

  1. The stand must be placed on a stable surface so as to prevent it from falling and injuring a person.
...read more.















































Calculating Uncertainties

To calculate the time period of 1 oscillation of the pendulum, one must first know the uncertainty of each measuring instrument used. The uncertainty of any instrument can be found through:

Uncertainty = Least Count2

This results in a least count of ±5.0 x 10-4 m for the meter ruler. The uncertainty of the stopwatch was calculated to be ±0.05seconds.

Now, to find the uncertainty of the time period of 1 oscillation, we must know that the time period = Average amount of time taken for 20 oscillation TAVG20

TAVG has an uncertainty of ±0.05 seconds.

Now, when we divide TAVG by 20, the following equation must be used to find the uncertainty:

Δ = uncertainty

x = TAVG

y = TAVG

R = value of TAVG ÷ 20 = Time period of one oscillation

ΔT = ±T (Δxx+ Δyy)


The relationship that we have to verify – as mentioned before – is as following.

t=-π2gdt+2π lg

As we must find a linear relationship, we need this equation to be made into the form y = mx +c. Therefore, let t = y and let dt= x. Now, the equation will look like the following:

y=-π2gx+2π lg

Now, it can be seen that this is a linear equation with gradient of -π2gand y-intercept of 2π lg

Now that we have this equation, we must plot dtin the x-axis and‘t’ in the y-axis.

The graph that follows on the next page shows the relationship between dt

...read more.


th oscillation is complete, then the error of reaction time will be eradicated. However, this is a very elaborate way to eliminate the problem, and is not an easy method to implement.

An easier, and more practical approach may be to use a different, more advanced set of stopwatches. These stopwatches would have increased respond time, and would respond to human input (pressing the ‘start’/’stop’ button) in a better and faster way. This would in turn increase the precision of the results, and would help make the results more reliable.

In addition to this, instead of 3 trials being conducted for each length, 5 trials should have been conducted; this would have resulted in more tests of the theory, and ultimately would have had the effect of creating more reliable, accurate, and valid results.

Also, at times, the standing clamp that was used got out of position, and became positioned at an angle. This would be an easy error to eradicate: standing clamps which are firmer, more rigid, and are less likely to move and shake during the experiment should be used. This will mean that the position of the stand will remain constant, and this is very important to the accuracy of the results.

To conclude, there were a few random and systematic errors present during this experiment, and these could have had a large impact on the final results. If these errors were eliminated, the experiment would become more reliable, and therefore, the results would become more accurate. This would mean that errors which may render a calculated gravitational acceleration at 11.61ms-2 would be eliminated, thus creating a better and more practical experiment.


[1] <http://en.wikipedia.org/wiki/Gravitation>

...read more.

This student written piece of work is one of many that can be found in our International Baccalaureate Physics section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related International Baccalaureate Physics essays

  1. Suspension Bridges. this extended essay is an investigation to study the variation in tension ...

    � 0.01 11.6 0.6440 � 0.005 129.4 6.1 0.8986 � 0.01 10 0.5492 � 0.005 Horizontal Distance (x) from the Rigid Support 1 � 0.05 (in cm) Length of the string = 148 cm Length of the string = 152 cm Vertical Distance (y1)

  2. In this extended essay, I will be investigating projectile motion via studying the movement ...

    The experimental values of range obtained are less than the corresponding theoretical values of range. This is mainly due to the air resistance. Thirdly, the trajectory of the projected metal ball clearly resembled a parabolic path, which matched with the description and characteristic of a typical projectile motion.

  1. This is a practical to investigate the relationship between time period for oscillations and ...

    the relation between time period and mass attached to the spring stands true. Regarding the controlled variables, I will be using the same spring throughout the experiment. Also, the clamp stand will be kept at the same position and the spring will be suspended from the clamp stand at the same height throughout the experiment.

  2. Investigate the factors affecting the period of a double string pendulum

    Thus when I will position my apparatus, the metal bar will be directly parallel to the clamp stands and the string perpendicular to the clamp stands and the metal bar. (6) Notes: the numbers at the end of each of the controlled variables refer to their illustration counter part on the next page.

  1. HL Physics Revision Notes

    The maximum amplitude is 2A at the antinodes. It is zero at the nodes. All points on the wave have the same amplitude Frequency All points oscillate with the same frequency All points oscillate with the same frequency Wavelength Twice the distance from one node to the next node Shortest

  2. Light Intensity Investigation

    the 10cm distance trials proved to obtain the highest light intensity (as hypothesized) at an average of 2614.33 Lux and the lowest readings were detected at the 100cm distance. Also, at each trial the readings were lower than those measured in all of the distances shorter than it.

  1. Investigation into the relationship between acceleration and the angle of free fall downhill

    line which means that the value of 1.11 m s-2 isn?t an incorrect value, leaving room for a possible systematic error. The results seem reasonable taken into account that the values measured were all relatively small, which can give a wider set of results.

  2. Investigating optical properties of Jelly.

    The thermometer was inserted into the top right corner of the Jelly. 9. The entire setup of Jelly in the low walled rectangular bowl was cooled to 10oC in the electronic water bath and the temperature was maintained until it was to be used again in step 12. 10.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work