ShilpaFlame Institute

11. The graph shows the behaviour of a length of wire in the region for which the substance obeys Hook’s law. P and Q represent

(a) P = applied force, Q = extension (b) P = extension, Q = applied force (c) P = extension, Q = stored elastic energy (d) P = stored elastic energy, Q = extension Answer-c (7)

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

(a) III only (b) II and III (c) I and III (d) I only Explanation-a (9)

5. 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

(a) Elasticity of wire P is maximum (b) Elasticity of wire Q is maximum (c) Tensile strength of R is maximum (d) None of the above is true Answer-d (4)

9. The adjacent graph shows the extension

The adjacent graph shows the extension (Δl) 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 …

8. The load versus elongation graph for four wires of the same material is shown in the figure. The thickest wire is represented by the line

(a) OD (b) OC (c) OB (d) OA Answer-a (12)

13. The value of force constant between the applied elastic force F and displacement will be

(a) √3 (b) 1/√3 (c) 1/2 (d) √3/2 Answer-b (5)

7. The stress versus strain graphs for wires of two materials A and B are as shown in the figure.

The stress versus strain graphs for wires of two materials A and B are as shown in the figure. If Y1 and Y2 are the Young ‘s modulii of the materials, then (a) YB = 2YA (b) YA …

3. In the above graph, point B indicates

(a) Breaking point (b) Limiting point (c) Yield point (d) None of the above Answer-c (12)

2. A graph is shown between stress and strain for a metal. The part in which Hooke’s law holds good is

(a) OA (b) AB (c) BC (d) CD Answer-a (8)

1. The graph shown was obtained from experimental measurements of the period of oscillations T for different masses M placed in the scale pan on the lower end of the spring balance. The most likely reason for the line not passing through the origin is that the

(a) Spring did not obey Hooke’s Law (b) Amplitude of the oscillations was too large (c) Clock used needed regulating (d) Mass of the pan was neglected Answer-d (5)

12. Assertion : Sterss is the internal force per unit area of a body. Reason : Rubber is less elastic than steel.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. (b) If both assertion and reason are true but reason is not the correct explanation of the assertion. (c) If assertion is …

11. Assertion : Identical springs of steel and copper are equally stretched. More work will be done on the steel spring. Reason : Steel is more elastic than copper.

2. Assertion : Spring balances show correct readings even after they had been used for a long time interval. Reason : On using for long time, spring balances losses its elastic strength.

10. Assertion : Young’s modulus for a perfectly plastic body is zero. Reason : For a perfectly plastic body, restoring force is zero.

9. Assertion : Two identical solid balls, one of ivory and the other of wet-clay are dropped from the same height on the floor. Both the balls will rise to same height after bouncing. Reason : Ivory and wet-clay have same elasticity.

8. Assertion : The bridges declared unsafe after a long use. Reason : Elastic strength of bridges losses with time.

7. Assertion : Strain is a unitless quantity. Reason : Strain is equivalent to force.

6. Assertion : Bulk modulus of elasticity (K) represents incompressibility of the material. Reason : Bulk modulus of elasticity is proportional to change in pressure.

5. Assertion : A hollow shaft is found to be stronger than a solid shaft made of same material. Reason : The torque required to produce a given twist in hollow cylinder is greater than that required to twist a solid cylinder of same size and material.

4. Assertion : Glassy solids have sharp melting point. Reason : The bonds between the atoms of glassy solids get broken at the same temperature.

3. Assertion : Steel is more elastic than rubber. Reason : Under given deforming force, steel is deformed less than rubber.

1. Assertion : The stretching of a coil is determined by its shear modulus. Reason : Shear modulus change only shape of a body keeping its dimensions unchanged.

8. An elastic material of Young’s modulus Y is subjected to a stress S. The elastic energy stored per unit volume of the material is

(a) 2Y/S2 (b) S2/2Y (c) S/2Y …

7.A particle of mass m is under the influence of a force F which varies with the displacement x according to the relation

A particle of mass m is under the influence of a force F which varies with the displacement x according to the relation F= -kx+Fº in which k and Fº are constants. The particle when disturbed will oscillate (a) about …

6. There are two wires of same material and same length while the diameter of second wire is 2 times the diameter of first wire, then ratio of extension produced in the wires by applying same load will be

(a) 1 : 1 (b) 2 : 1 (c) 1 : 2 (d) 4 : 1 Answer-d (3)

5. 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 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 3L/4 from its lower end is

(a) W1/S (b) W1 +(W/4) / S (c) W1+(3W/4) / S (d) (W1+W)/S Answer-c …

4. The extension in a string obeying Hooke’s law is x. The speed of sound in the stretched string is v. If the extension in the string is increased to 1.5x, the speed of sound will be

(a) 1.22 v (b) 0.61 v (c) 1.50 v (d) 0.75 v Answer-a (7)

3. Two rods of different materials having coefficients of linear expansion

3. Two rods of different materials having coefficients of linear expansion α1,α2 and Young’s moduli Y1 and Y2 respectively are fixed between two rigid massive walls. The rods are heated such that they undergo the same increase in temperature. There …

2. To break a wire, a force of

2. To break a wire, a force of 106 N/m2 is required. If the density of the material is 3×103 Kg/cm3 , then the length of the wire which will break by its own weight will be (a) 34 m …

1. An Indian rubber cord L metre long and area of cross-section

An Indian rubber cord L metre long and area of cross-section A metre 2 is suspended vertically. Density of rubber is D Kg/metre 3 and Young’s modulus of rubber is E newton/metre 2 . If the wire extends by l metre under …