Tiêu đề Mechanical Properties of Solids.pdf ✅

CHAPTER MECHANICAL PROPERTIES OF SOLIDS 8 Exercise 1: NCERT Based Topic-wise MCQs 8.1 INTRODUCTION 1. What is the phenomenon of temporary delay in regaining the original configuration by an elastic body, after the removel of a deforming force? NCERT Page-235 / N-167 (a) Elastic fatigue (b) Elasticity (c) Plasticity (d) Elastic after effect 2. When forces are applied on a body such that it is still in static equilibrium, then the extent to which the body gets deformed, depends on NCERT Page-235 / N-167 (a) nature of the material (b) magnitude of deforming force (c) Both (a) & (b) (d) None of these ELESTIC BEHAVIOUR OF SOLIDS 3. The force exerted by a special compression device is given as function of compression x as Fx(x) = kx(x − l) for 0 ≤ x ≤ l, where l is maximum possible compression and k is a constant. The force exerted by the device under compression is maximum when compression is - NCERT Page-236 (a) 0 (b) l/4 (c) l/√2 (d) l/2 4. The potential energy U between two atoms in a diatomic molecules as a function of the distance x between atoms has been shown in the figure. The atoms are NCERT Page-236 (a) attracted when x lies between A and B and are repelled when x lies between B and C (b) attracted when x lies between B and C and are repelled when x lies between A and B (c) are attracted when they reach B from C (d) are repelled when they reach B from A
8.2 STRESS AND STRAIN 5. A 2m long rod of radius 1cm which is fixed from one end is given a force of 8N. The longitudinal strain developed will be [take γ = 2.5 × 1011N/m2 ] NCERT Page-236 / N-168 (a) 10−8 (b) 10−6 (c) 10−5 (d) 10−4 6. The restoring force per unit area is known as NCERT Page-236 / N-168 (a) strain (b) elasticity (c)stress (d) plasticity 7. In magnitude hydraulic stress is equal to NCERT Page-237, 238 / N-169 (a) hydraulic force (c). restoring force (b) hydraulic pressure (d) hydraulic strain 8. Substances which can be stretched to cause large strains are called NCERT Page-239 / N-168 (a) brittle (c) plastic (b) ductile (d) elastomer 9. The reason for the change in shape of a regular body is NCERT Page-237 / N-168 (a) volume stress (c) longitudinal strain (b) shearing strain (d) metallic strain 10. Longidudinal stress depends on NCERT Page-236 / N-168 (a) area (b) length (c) volume (d) mass 11. Which of the following types of stress causes no change in shape? NCERT Page-237, 238 / N-169 (a) compressive stress (c) oblique stress (b) hydraulic stress (d) none of these 12. An elevator cable is to have a maximum stress of 7 × 107N/m2 to allow for appropriate safety factors. Its maximum upward acceleratiom is 1.5m/s 2 . If the cable has to support the total weight of 2000kg of a loaded elevator, the area of crosssection of the cable should be NCERT Page-236 / N-168 (a) 3.28cm2 (c) 0.328cm2 (b) 2.38cm2 (d) 8.23cm2 13. To break a wire, a force of 106N/m2 is required. If the density of the material is 3 × 103kg/m3 , then the length of the wire which will break by its own weight will be NCERT Page-236 / N-168
(a) 34m (b) 30m (c) 300m (d) 3m 14. A light rod of length 2m suspended from the ceiling horizontally by means of two vertical wires of equal length. A weight W is hung from a light rod as shown in figure. The rod hung by means of a steel wire of cross-sectional area A1 = 0.1cm2 and brass wire of cross-sectional area A2 = 0.2cm2 . To have equal stress in both wires, T1/T2 = (a) 1/3 NCERT Page-236 / N-168 (b) 1/4 (c) 4/3 (d) 1/2 15. A force of 6 × 106Nm−2 is required for breaking a material. Then density ρ of the material is 3 × 103kgm−3 . If the wire is to break under its own weight, the length of the wire made of that material should be (take g = 10ms−2 ) (a) 20m NCERT Page-236 / N-168 (b) 200m (c) 100m (d) 2000m 8.3 HOOKE’S LAW 16. According to Hooke's law of elasticity, if stress is increased, then the ratio of stress to strain (a) becomes zero NCERT Page-238 / N-169 (c) decreases (b) remains constant (d) increases 17. Which of the following affects the elasticity of a substance? NCERT Page-238 / N-169 (a) Hammering and annealing (b) Change in temperature (c) Impurity in substance (d) All of the above 18. The length of a metal is l1 when the tension in it is T1 and is l2 when the tension is T2. The original length of the wire is NCERT Page-238 / N-169 (a) l1+l2 2 (b) l1T2+l2T1 T1+T2 (c) l1T2−l2T1 T2−T1 (d) √T1T2l1l2 19. The length of an elastic string is a metre when the longitudinal tension is 4N and b metre when the longitudinal tension is 5N. The length of the string in metre when the longitudinal tension is 9N is NCERT Page-238 / N-169
(a) a − b (b) 5b − 4a (c) 2b − 1 4 a (d) 4a − 3b 20. A wire of length L is hanging from a fixed support. The length changes to L1 and L2 when masses 1kg and 2kg are suspended respectively from its free end. Then the value of L is equal to: NCERT Page-238 / N-169 (a) √L1L2 (b) L1+L2 2 (c) 2L1 − L2 (d) 3L1 − 2L2 21. The area of cross-section of the rope used to lift a load by a crane is 2.5 × 10−4m2 . The maximum lifting capacity of the crane is 10 metric tons. To increase the lifting capacity of the crane to 25 metric tons, the required area of crosssection of the rope should be : ( take g = 10ms−2 ) NCERT Pagé-238 / N-169 (a) 6.25 × 10−4m2 (b) 10 × 10−4m2 (c) 1 × 10−4m2 (d) 1.67 × 10−4m2 8.4 STRESS-STRAIN CURVE 22. If the load is increased beyond the point, the strain increases rapidly for even a small change in the stress. (a) elastic point NCERT Page-238 / N-169 (c) plastic point (b) yield point (d) fracture point 23. The graph given is a stress-strain curve for NCERT Page-239 / N-169 (a) elastic objects (b) plastics (c) elastomers (d) None of these 24. 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 corss-sectional area