# State and verify Hooke’s Law

See Hooke’s law here

Aim To state and verify Hooke’s Law
Apparatus a clamp stand, half meter ruler, helical spring, mass hanger etc.
Formula Hooke’s law state that the stress applied to a material is proportional to the strain on that material. Hooke’s law generally holds only up to the elastic limit of stress for that material.
Figure
Procedure An initial reading was taken when only the mass hanger was suspended from the spring.A 50g mass was then carefully slotted onto the hanger and the reading was recorded.This step was repeated with more 50g masses until 400g had been added to the hanger.

The whole experiment was repeated after adjusting the position of the ruler.

Observations  Initial length of the spring ………….. cm

 S.No Mass added tothe hanger (g) Weight(N) Ruler reading (cm) Extension(cm) 1 50 2 100 3 150 4 200 5 250 6 300 7 350
Graph  A graph was plotted of the weight added to the hanger against the extension of the spring. The points of both sets of results were plotted on the one graph. This gave us a scatter graph of the results. It showed us not only the trend of the results but also how precise our readings were. A key explaining ‘which set was which’ was written on the graph.The title of the graph indicated what the experiment involved – it did not just say what was plotted angainst what – that could be seen from the labelling of the axes!A best fit line was plotted. These points indicated a trend of proportionality so a smooth straight line was drawn. It did not matter whether it went through all of the points. What mattered was that it showed the general pattern that the results indicated.

Precautions
• The ruler was carefully viewed from all angles to ensure that it was vertical
• pointer was used to help read the scale on the ruler. The scale had to be viewed at eye level to avoid parallax error.
• The experimenter had to be sure the spring system was stationary before a reading was taken.
• At the end of each set of readings, the position of the ruler was adjusted before the experiment was repeated. This was to avoid ‘repeat’ errors
Result  Hooke’s law is verified and the spring constant is calculated from the graph.