Title 09. MECHANICAL PROPERTIES OF SOLIDS.pdf ✅

PAPER 1 (1.) The following four wires of length L and radius r are made of the same material. Which of these will have the largest extension when the same tension is applied : (1) L 50 cm,r 0.25 mm = = (2) L 100 cm,r 0.5 mm = = (3) L 200 cm,r 1 mm = = (4) L 300 cm,r 1.5 mm = = (2.) The rubber cord of a catapult is pulled back until its original length has been doubled. Assuming that the cross-section of the cord is 2 mm square and that Y for rubber is 7 2 1 10 N / m  what is the tension in the cord : (1) 20 N (2) 40 N (3) 74 N (4) 60 N . (3.) Which of the following is most elastic : (1) Steel (2) Plastic (3) Rubber (4) Mud ball (4.) The reciprocal of bulk modulus of a substance is called its : (1) Modulus of elasticity (2) Compressibility (3) Rigidity (4) Viscosity (5.) Solids are capable of : (1) Longitudinal strain only (2) Longitudinal and shearing strains (3) Longitudinal, shearing and volume strains (4) Volume strain only. (6.) Which elasticity is associated with liquids : (1) Young's modulus (2) Modulus of rigidity (3) Volume elasticity (4) None of these. (7.) Which one of the following is the Young's modulus (in 2 N / m ) for the wire having the stress-strain curve shown in figure : (1) 11 24 10  (2) 11 8.0 10  (3) 11 10 10  (4) 11 2.0 10  .
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(8.) A substance breaks down by a stress of 6 10 newton per metre 2 . If the density of the material of the wire is 3 3 10 kg  per metre 3 , then the length of the wire of that substance which will break under its own weight when suspended vertically is : (1) 3.4 m (2) 34 m (3) 340 m (4) 3400 m (9.) A steel wire is suspended vertically from a rigid support. When loaded with a weight in air, it extends by a I and when, the extension is reduced to w I (when emriging in a water). Then the relative density of the material of the weight is : (1) a w l I (2) a a w I I I − (3) w a w I I I − (4) w a l l (10.) A wire can sustain the weight of 20 kg before breaking. If the wire is cut into two equal parts, each part can sustain a weight of : (1) 10 kg (2) 20 kg (3) 40 kg (4) 80 kg . (11.) A wire elongates by 1.0 mm when a load W is hanged from it. If the wire goes over a pulley and two weights W each are hund at the two ends the elongation of the wire will be : (1) 0.5 mm (2) 1 mm (3) 2.0 mm (4) 4.0 mm (12.) One end of a uniform wire of length L and of weight W is attached rigidly to a point in the roof and a weight W1 is suspended from its lower end. If S is the area of cross-section of the wire, the stress in the wire at a height 3 / 4 L from its lower end is : (1) W1 S (2) 1 4 W W S     +   (3) 1 3 4 W W s     +   (4) (W W 1 ) S + (13.) Which of the following is NOT the reason for calling steel more elastic than rubber : (1) For given load there is more strain in rubber is steel (2) Young's modulus for steel is much larger than that for rubber (3) For given strain, there is more stress in steel than in rubber (4) Steel wire returns to original length when load is removed but rubber does not do so (14.) An alastic metal rod will change its length when it : (1) Falls vertically under its weight (2) Is pulled along its length by a force acting at one end (3) Rotates about an axis at one end (4) Slides on a rough surface
(15.) The wires A and B show in the figure are made of the same material and have radii A r and B r respectively. The block between them has a mass m . When the force F is mg / 3 , one of the wires breaks : (1) A will break before B if A B r r = (2) A will break before B if 2 A B r r  (3) Either A or B may break if 2 A B r r = (4) The lengths of A and B must be known to predict which have will break Direction for 16 and 17 Two equal and opposite force F and −F act on A rod of uniform cross sectional area A , as shown in figure (16.) Longitudinal stress on the section AB is (1) 2 sin F A  (2) F sin A  (3) cos F A  (4) sin cos F A   (17.) Longitudinal stress will be maximum when  (1) 45 (2) 30 (3) 90 (4) 60 (18.) The diagram shows the change x in the length of a thin uniform wire caused by the application of stress F at two different temperatures T1 and T2 . The variations shown suggest that: