A steel spring, a 100g mass hanger, 12, 100g masses, a retort stand, a boss and clamp, a clamp, a metre rule, an s-hook, a pointer, safety goggles, a slotted base.
The main cause of error in this experiment is reading the stretched length of the spring.
The metre rule scale should be read at eye level directly opposite the pointer.
Use the slotted base to ensure that the metre rule is vertical.
Initial length of the spring = X cm.
|Mass in kg||Stretching force (F in N)||Stretched length in cm||Extension e in cm|
Plot a graph of stretching force, F in N on the y-axis, against extension, e in cm on the x-axis.
Join the points with a line of best fit.
We can see from the graph that as the stretching force increases the extension of the spring also increases. This agrees with our prediction.
In fact, since the line of best fit is a straight line through the origin, up to a certain point, we can be even more precise.
We can say that the stretching force F is directly proportional to the extension e up to a limit known as the limit of proportionality.
This is known as Hooke’s law.
Stretching force F=spring constant k x extension e
F = ke
The gradient of the graph = = spring constant k
Calculate the gradient of the line.