Helical Spring

Materials required

•     A spring
•     A rigid support
•     Weight hanger
•     50g or 20 g slotted weights
•     A vertical wooden scale
•     A fine pointer

Real Lab Procedure

1. The helical spring is suspended vertically from a rigid support.A pointer is attached horizontally at the free end of the spring.
2. A metre scale is kept vertically in such a way that the tip of the pointer is over the divisions of the scale, but does not touch the scale.
3. A dead weight, w0 gwt is suspended by the weight hanger to keep the spring vertical. The reading of the pointer on the metre scale is noted.
4. Now, gently add a suitable load of 50 g slotted weights to the hanger and the reading of the pointer is noted.
5. The weights are added one by one till the maximum load is reached. In each case, the reading of the pointer is noted.
6. The weights are then removed one by one and the reading of the pointer is noted in each case of unloading.
8. From this, extension, l (in m) for the loads (w0+50), (w0+100), (w0+150)   etc. , are calculated as (z1-z0), (z2-z0), (z3-z0) respectively.
9. In each case, k =mg/l is calculated. The average value of k gives the spring constant in N/m.
10. A graph is drawn with load M in kg wt along X axis and extension, l in metre along the Y axis. The graph is a straight line. The reciprocal of the slope of the graph is determined. It gives spring constant in kg wt/m. The spring constant in N/m is obtained by multiplying this with g=9.8 m/s2.

Simulator Procedure (As performed through the Online labs)

Select the spring for which the spring constant is to be measured, from the 'Select Spring’ drop down list.
Select the environment to perform the experiment from the 'Choose Environment' drop down list.
Use the ‘Change hanging mass’ slider to change the mass attached at the end of the spring.
The spring elongates or compresses according to the addition or removal of mass attached at its end.
The elongation or compression of the spring is noted in the scale by using the position of the pointer attached at the end of the spring.
Now, calculations are done as per the observation column and the spring constant of the selected spring can be found out.
Enable the ‘Show result’ checkbox to view the spring constant of the selected spring.
Click on the ‘Reset’ button to redo the experiment.

Observations:

 Serial No of Obs. Load on hanger(W) = applied force (F)(kg wt) Tension= Mg (N) Reading of position of pointer tip Extension l= z x 10-2 (m) $k=\frac{mg}{l}$N/m Loading X(cm) Unloading Y(cm) Mean,$z=\frac{x+y}{2}$ (cm) Dead load(W0) (W0+ .05) (W0+.1) (W0+.15) (W0+.2) (W0+.25) (W0+.3)

Mean k=…………N/m.

Spring constant, k from load extension graph

AB=---------kg wt
BC=---------m
$k=\frac{AB}{BC}\times g$  =  ---------Nm-1

Result

By calculation, the force constant of the given spring = .............N/m.
From load-extension graph, the force constant of the given spring =……….N/m

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