Physics-DPP-2-Properties of Matter

PHYSICS Topic: PROPERTIES OF MATTER Date: 1. Two wires of the same material (Young’s modulus = Y) and same length L but radii R and 2 R respectively are joined end to end and a weight W is suspended from the combination as shown in the figure. The elastic potential energy in the system is (a) 3W2L 4πR2Y (b) 3W2L 8πR 2Y (c) 5W2L 8πR 2Y (d) W2L πR 2Y 2. A uniform elastic plank moves due to a constant force F placed over a smooth surface. The area of end face is S and Young’s modulus of the material is E. What is average strain produced in the direction of the force ? (a) F SE (b) F 2SE (c) F 4SE (d) zero 3. What is the approximate change in density of water in a lake at a depth of 400 m below the surface ? The density of water at the surface is 1030 kg/m2 and bulk modulus of water is 2 × 109 N/m2 : (a) 4 kg /m3 (b) 2 kg / m3 (c) 6 kg / m3 (d) 8 kg /m3 4. A wire is elongated by 2 mm when a brick is suspended from it. When the brick is immersed in water, the wire contracts by 0.6 mm. What is the density of brick ? (a) 3333 kg /m3 (b) 4210 kg / m3 (c) 5000 kg / m3 (d) 2000 kg / m3 5. A uniform pressure P is exerted on all sides of a solid cube at temperature toC. By what amount should the temperature be raised in order to bring the volume back to that it had been before the pressure was applied. (Linear expansivity of the material of the cube is α and the bulk modulus of elasticity is β ) (a) Pα β (b) 3Pα β (c) P αβ (d) P 3αβ 6. The temperature of a wire of length 1 m and area of cross-section 1 cm2 is increased from 0oC to 100oC. If the rod is not allowed to increase in length, the force required will be : (α = 10–5 / o C and Y = 1011 N/m2 ) (a) 103 N (b) 104 N (c) 105 N (d) 109 N 7. The stress versus strain graphs for wires of two materials A and B are as shown in the figure. If YA and YB are the Young’s modullii of the materials, then : (a) YB = 2 YA (b) YA = YB (c) YB = 3 YA (d) YA = 3 YB 8. 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 of Q is maximum (c) tensile strength of R is minimum (d) none of the above is true PHYSICS Topic: PROPERTIES OF MATTER Date: 9. An iron rod of length 2 m and area of cross-section 50 mm2 stretches by 0.5 mm when a mass of 250 kg is hung from its lower end. The Young’s modulus of iron rod is : (a) 19.6 × 1020 N/m2 (b) 19.6 × 1018 N/m2 (c) 19.6 × 10`1 N/m2 (d) 19.6 × 1010 M/m2 10. For a wire of length l, maximum change in length under stress condition is 2 mm. What is the change in length under same conditions when length of wire is halved ? (a) 1 mm (b) 2 mm (c) 4 mm (d) 8 mm PHYSICS Topic: PROPERTIES OF MATTER Date: Answer Key 1. (c) 2. (b) 3. (b) 4. (b) 5. (d) 6. (b) 7. (d) 8. (d) 9. (d) 10. (a)