The upper end of a wire of radius 4 mm and length 100 cm is clamped and its other end is twisted through an angle of 30°. Then angle of shear is

(1) $12°$                                     

(2) $0.12°$

(3) $1.2°$                                     

(4) $0.012°$

A rod of length l and radius r is joined to a rod of length l/2 and radius r/2 of same material. The free end of small rod is fixed to a rigid base and the free end of larger rod is given a twist of $\theta$, the twist angle at the joint will be 

(a) $\theta /4$                          (b) $\theta /2$

(c) $5\theta /6$                         (d) $8\theta /9$

Shearing stress causes a change in-

(1)   Length                              

(2)   Breadth

(3)   Shape                               

(4)   Volume

To break a wire, a force of ${10}^{6}N/m^2$ is required. If the density of the material is $3\times {10}^3 kg/m^3$, then the length of the wire which will break by its own weight will be -

(a) 34 m                             (b) 30 m

(c) 300 m                            (d) 3 m

The strain-stress curves of three wires of different materials are shown in the figure. P, Q and R are the elastic limits of the wires. The figure shows that:
           

The diagram shows a force-extension graph for a rubber band. Consider the following statements

I. It will be easier to compress this rubber than expand it

II. Rubber does not return to its original length after it is stretched

III. The rubber band will get heated if it is stretched and released

 Which of these can be deduced from the graph?

(1)   III only                              

(2)   II and III

(3)   I and III                            

(4)   I only

The adjacent graph shows the extension $\left(∆l\right)$ of a wire of length 1m suspended from the top of a roof at one end with a load W connected to the other end. If the cross sectional area of the wire is ${10}^{-6}{m}^2$ calculate the young’s modulus of the material of the wire

(a) $2\times {10}^{11}N/m^2$

(b) $2\times {10}^{-11}N/m^2$

(c) $3\times {10}^{-12}N/m^2$

(d) $2\times {10}^{-13}N/m^2$

The diagram shows stress v/s strain curve for the materials A and B. From the curves we infer that

(1) A is brittle but B is ductile  

(2) A is ductile and B is brittle

(3) Both A and B are ductile      

(4) Both A and B are brittle

If the potential energy of a spring is V on stretching it by 2 cm, then its potential energy when it is stretched by 10 cm will be

(1) V/25                                   

(2) 5V

(3) V/5                                    

(4) 25V

Two wires of same diameter of the same material having the length l and 2l. If the force F is applied on each, the ratio of the work done in the two wires will be

(1) 1 : 2                                   

(2) 1 : 4

(3) 2 : 1                                   

(4) 1 : 1