Hooke's law states that the extension produced in the wire is directly proportional to the load applied within proportional limit. Later on it was found that this law is applicable to all types of deformations such as compression, bending, twisting etc. and thus a modified form of Hooke's law was given as stated below.
“With-in proportional limit, the stress developed is directly proportional to the strain produced in a body”
i.e. stress ∝ strain or stress = E x strain
where E is a constant known as modulus of elasticity, which depends upon the nature of the material of the body and the manner in which the body is deformed.
Experimental verification of Hook’s law
Suspend a spring from a rigid support. Attach a scale pan and a light point at its lowest end. The pointer can slide over a vertical scale graduated in centimetre. Note the reading on the scale. Add a 5 gm weight in the pan and note reading. The difference of the two readings gives the extension produced. The same procedure should be repeated with every additional 5g weight.
It will be observed that the extension is directly proportional to load. This verifies Hook’s law.
