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

Centripetal motion. The objective of this experiment is to verify whether the tension in a centripetal force apparatus is equal to the weight of the mass.

Extracts from this document...


Physics Laboratory Report

Centripetal motion

Aim of experiment:

The objective of this experiment is to verify whether the tension in a centripetal force apparatus is equal to the weight of the mass.


(Fig. 1)image01.jpg

Fig. 2 shows an object of mass m moving with constant velocity v in a circular path of radius r.

By keeping the angular speed of the rubber bung constant and considering the equilibrium of all the applied forces in the system, the theoretical value of the centripetal force F is calculated as follows:

F = mv2/r                or     F = mrω2

where v and ω are the linear and angular speeds of the object respectively.

Nevertheless, some correction should be made in this experiment. In this experiment, the following set-up is used.


As shown in Fig.3, in reality, the string is not horizontal and moves in a circle of radius r = l sinθ. The weight of the hanger with slotted mass gives the tension (T) in the string.


The horizontal component of the tension provides the net centripetal force. Therefore,

T sinθ = mrω2

T sinθ = m(l sinθ)ω2

T = mlω2


Rubber bung                        x 1

Glass tube (15cm long)        x 1

Nylon thread (1.5m)        x 1

Slotted mass (50g)                x 4

Hanger (150g)                        x 1

Paper clip                        x 1

Meter rule                        x 1

Stop watch                        x 1

Adhesive tape                        x 1

Balance                                x 1


  1. The mass of the rubber bung (m)
...read more.


Data and data analysis:

Mass of the rubber bung (m) = 0.0211kg ± 0.00005kg

Length of the nylon thread (l) = 0.800m ± 0.0005m

Take g = 9.81ms-2

Hanger with slotted masses

Time taken for complete revolutions / s

Angular speed / rad s-1

(± 0.05 rad s-1)

Tension / N

(± 0.10055 N)

Mass (M) / kg

Weight (W= Mg) / N

30t (± 0.05s)


(± 0.00167s)

ω = 2π/t

T = mlω2

1st set

2nd set

3rd set















































With M = 0.15kg,

Absolute difference between W and T = 1.52 – 1.4715 = 0.0485N

        Percentage difference between W and T = 0.0485/1.4715 x 100% ≈ 3.30%

With M = 0.20kg,

Absolute difference between W and T = 1.9620 – 1.96 = 0.0020N

        Percentage difference between W and T = 0.0020/1.9620 x 100% ≈ 0.102%

With M = 0.25kg,

Absolute difference between W and T = 2.4525 – 2.19 = 0.2625N

...read more.



From the results obtained, it can be easily seen that the differences between the tension of the string and the centripetal force of the circular motion of the rubber bung are 3.30%, 0.102%, 10.7%, 10.6% and 9.13%, with varying mass(M) and hence tension(T) used. It actually does not show much difference between the two values. The errors are indeed caused by the matters stated in ‘Sources of error’. Consequently, it can be concluded that the tension (T) of the string is approximately the same as the weight (W) used.

Furthermore, we cannot circle the rubber bung exactly in a horizontal plane. As shown in Fig.3, if the rubber bung is circled in a horizontal plane, the tension (T) of the string will no longer contribute a vertical force component to balance the weight (W) of the rubber bung. Hence, there will not be any force to balance the weight of the rubber bung. Consequently, the rubber bung must make an angle θ, which is more than or less than 90o, with the vertical, and thus the rubber bung cannot circle in a horizontal plane.


From the experiment, as the tension (T) of the string is approximately the same as the weight (W) used, it can be verified that the tension in a centripetal force apparatus is equal to the weight of the mass.


...read more.

This student written piece of work is one of many that can be found in our AS and A Level Mechanics & Radioactivity 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 AS and A Level Mechanics & Radioactivity essays

  1. Force of Friction experiment

    Effect of surface area on friction Theoretically, friction is independent of contacting area. The result should be the same when the blocks are arranged side by side and piled up. However experimental results show that friction when side by side is slightly greater than that when piled up.

  2. Flywheel experiment

    Actual value)/ Expected Value] x 100 = [3.4x10-2/ 3.43x10-2] x 100 = 99.13% 5. DISCUSSIONS/CONCLUSION Following the analysis of my results, the values of Iexperiment and Itheory differ by fairly a significant amount i.e. (a percentage error of 99.13%). The errors that led to the difference in the two values

  1. According to Newton's first law, an object in motion continues in motion with the ...

    Galileo further observed that regardless of the angle at which the planes were oriented, the final height was almost always equal to the initial height. If the slope of the opposite incline was reduced, then the ball would roll a further distance in order to reach that original height.

  2. Use of technology in a hospital radiology department. The department of imaging is one ...

    Even small levels can penetrate air. Paper or thin metal. High level can only be stopped by many centimetre of lead or many metres of concrete. [ 11 ] The below picture shows us how this radioactive source absorb by different martial Figure 4 [12] The degree to which each

  1. Young's Modulus of Nylon

    By calculating engineering stress, the effect of this variable can be negated. Safety Whilst the practical side of this investigation does not include any particularly dangerous apparatus or methods, there are still some safety considerations to be taken. Eye protection will have to be worn whilst the nylon has stress

  2. The physics involved with a rollercoaster.

    Since the PE depends on height and the KE depends on velocity, so the cars has low speed at top of the hill and high speed at bottom of the loop. The acceleration peaks when all the cars are headed downward.

  1. Investigating the factors affecting tensile strength of human hair.

    This could make my tensile stress values incorrect. My conclusion therefore could be affected; by making out that a certain coloured hair had a higher tensile stress than another coloured hair, when really it shouldn't have. This would make my conclusion unreliable. * There were different shades of hair colour, for example, there were light brown hair colours and dark brown hair colours.

  2. The aim of this experiment is to test whether or not a Crunchie bar ...

    25mm = 3500mm To use the stress formula the surface area needs to be in m , to get this I will: 3500 x 1000000 = 0.0035m As I have used three crunchie bars I will need to times the above value by 3: 0.0035 x 3 = 0.0105m Using the above results table I have constructed a graph.

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