This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Elasticity”.
1. When too many people stand on a bridge it collapses, why?
a) Due to increase in stress
b) Due to overweight
c) Due to improper construction
d) Due to friction
Explanation: Stress is the force per unit area experienced by the body and strength is the ability to withstand the stress. When stress becomes greater than strength, accidents happen.
2. For a constant force, a rope breaks due to stress. Which of the following is useful to reduce the stress?
a) Increase the length of the rope
b) Apply small force
c) Increase the cross sectional area of the rope
d) Use a different material of rope
Explanation: Stress = Force/Area
For a constant force, if the area is small, stress is large. If the area is large, stress is small. Therefore by increasing the cross sectional area stress can be reduced considerably.
3. When a rope is pulled on either side, what is the stress acting on it?
a) Compressive stress
b) Tensile stress
c) Normal stress
d) Tangential stress
Explanation: A tensile stress occurs when something is being pulled. A rope experiences tensile stress because it is flexible. In other words, a rope cannot be pushed.
4. Fluids cannot resist sheer stress.
Explanation: Fluids cannot resist sheer stress because they do not deform. Rather they flow. Fluids are opaque to transverse waves therefore they have the inability to undergo sheering stress.
5. What happens when the stress applied to the body is increased beyond the maximum value and is removed after some time?
a) The body will come back to its original position
b) The body will oppose the stress
c) The body becomes hot
d) The body cannot return to its original position
Explanation: When the applied stress exceeds the maximum value the body does not regain its original position completely after removing external forces. It is said to have reached its elastic limit.
6. A pendulum A oscillating continuously comes to rest after some time. Now make both pendulums A and B to oscillate simultaneously. What will happen?
a) A comes to rest earlier than B
b) B comes to rest earlier than A
c) A and B comes to rest simultaneously
d) A and B oscillate forever
Explanation: If a body is subjected to stress or strain continuously if becomes weak due to elastic fatigue. Therefore A comes to rest earlier than B.
7. What will happen to the elastic property of Gold when Potassium is added to gold?
a) The elastic property of gold decreases
b) The elastic property of gold remains unaltered
c) The elastic property of gold increases
d) Gold loses its elastic property
Explanation: The addition of impurities causes variation in the elastic property of materials. Potassium when added to gold increases its elasticity thereby making it easy to be electroplated.
8. A copper wire of length 3m and 1mm diameter is subjected to a tension of 5N. Calculate the elongation produced, if the young’s modulus of copper is 120GPa
c) 0.125 ×10-3 m
Explanation: Young’s modulus = (Force ×Length)/(Area ×Elongation); Area=πr2
Elongation = (Force ×Length)/(Area ×Young’s modulus)
Elongation = 15.9mm.
9. The modulus of rigidity and Poisson’s ratio of the wire are 2.87 × 1010 N/m2 and 0.379 respectively. What is the value of young’s modulus of the material of the wire.
a) 1.08773 × 1010 N/m2
b) 7.915 × 1010 N/m2
c) 7.5725 × 1010 N/m2
d) 0.1403 × 1010 N/m2
Explanation: Poisson’s ratio = Y/2n – 1
Y=7.915 × 1010 N/m2.
10. What is the effect of hammering on elasticity of materials?
a) Has no effect on elasticity
b) Decreases the elasticity
c) Increases the elasticity
d) Breaks the material
Explanation: While being hammered or rolled, crystals break into smaller units resulting in increase of their elastic properties.
11. Calculate the Young’s modulus in the cantilever depression method. The length is 1m which is suspended with a load of 150gm. The depression is found to be 4cm. The thickness of the beam is 5mm and breadth is 3cm.
a) 3.92 × 1010 N/m2
b) 9000 × 1010 N/m2
c) 4000 × 1010 N/m2
d) 1.245 ×1010 N/m2
Explanation: Y = (4gl3)/(bd2 ) × M/y
Y = 3.92 × 1010 N/m2.
12. What is the effect of annealing on elasticity of materials?
a) Increases the elasticity
b) Decreases the elasticity
c) Has no effect on elasticity
d) Distorts the material
Explanation: Annealing is the process of heating a material and then gradually cooling it. While annealing, constituent crystals are uniformly oriented and form larger crystal grains, which results in decrease in their elastic properties.
13. A thick wire is suspended from a rigid support and no load is attached to its free end but the wire is under stress.
Explanation: The wire is maybe suspended with no load but the wire will experience some stress due to its own weight. Therefore the answer is true.
14. Which type of elasticity is involved in tangential push on the upper face of a block?
a) Bulk modulus
b) Young’s modulus
c) Rigidity modulus
d) Elastic limit
Explanation: Rigidity modulus is defined as the ration between tangential stress and shearing strain. When a tangential stress is applied to the upper face of a block, the cube gets deformed and there is relative displacement.
15. Air is more elastic than water.
Explanation: Air can be compressed easily while water is incompressible and bulk modulus is reciprocal of compressibility. Therefore, water is more elastic than air.
Sanfoundry Global Education & Learning Series – Engineering Physics.
To practice all areas of Engineering Physics, here is complete set of 1000+ Multiple Choice Questions and Answers.