Mechanical Properties of Solids MCQs for NEET — Physics Questions with Answers

(a) 

$$\begin{gathered} Energy per unit volume =\frac{{\left(stress\right)}^2}{2Y} \\ \frac{E_1}{E_2}=\frac{Y_2}{Y_1} \left(Stress is cons\tan t\right)\therefore \frac{E_1}{E_2}=\frac{3}{2} \end{gathered}$$

(a)

 $$\begin{gathered} Energy per unit volume =\frac{1}{2}\times Y\times {\left(strain\right)}^2 \\ \therefore strain=\sqrt{\frac{2E}{Y}} \end{gathered}$$

(b) $U=\frac{F^2}{2K}=\frac{T^2}{2K}$

(c)

$$\begin{gathered} W = \frac{1}{2}\times \frac{AY}{L}\times {\left(x\right)}^2 \\ Where x is deformation \end{gathered}$$

(b)

Due to stretching, potential energy is stored in the rubber band which is released on releasing the rubber. Thus, potential energy is increased.

(a) $W=\frac{1}{2}Fl=\frac{1}{2}\times Mg\times l=\frac{1}{2}\times 5\times 10\times 3=75 J$

(b) $$\begin{gathered} U=\frac{1}{2}\times Y\times {\left(Strain\right)}^2=\frac{1}{2}\times 9\times {10}^{11}\times {\left(\frac{1}{100}\right)}^2 \\ =4.5\times {10}^7 J \end{gathered}$$

According to the NCERT text, 'From the graph, we can see that in the region between O to A, the curve is linear. In this region, Hooke’s law is obeyed. The body regains its original dimensions when the applied force is removed. In this region, the solid behaves as an elastic body.'

The NCERT states, 'The point B in the curve is known as yield point (also known as elastic limit) and the corresponding stress is known as yield strength (σy) of the material.'

The NCERT text explains, 'If the load is increased further, the stress developed exceeds the yield strength and strain increases rapidly even for a small change in the stress. The portion of the curve between B and D shows this. When the load is removed, say at some point C between B and D, the body does not regain its original dimension. In this case, even when the stress is zero, the strain is not zero. The material is said to have a permanent set. The deformation is said to be plastic deformation.' This indicates that permanent deformation (plastic deformation) starts to occur if the material is stressed beyond point B.