9

Q1. Elastic limit point on the stress-strain curve appears

• after proportionality limit
• before proportionality limit
• at the location same as proportionality limit
• cannot predict where it appears along the graph

Solution

Elastic limit point appears before the proportionality limit point along the stress-strain curve.

Q2. When a 13.2 kg mass is placed on top of a vertical spring, the spring compresses by 5.93 cm. Find the force constant of the spring.

• 3085 N/m
• 2175 N/m
• 2281 N/m
• 3181 N/m

Solution

Q3. Modulus of rigidity is defined as the

• ratio of normal stress to tangential strain
• ratio of normal stress to sheer strain
• ratio of tangential stress to tangential strain
• ratio of tangential stress to sheer strain

Solution

Modulus of rigidity is defined as the ratio of tangential stress to sheer strain.

Q4. The length of the wire is increased by 1 mm on the application of a given load. In a wire of the same material but of length and radius twice that of the first, on application of the same force, extension produced is

• 2 mm
• 0.5 mm
• 4 mm
• 0.25 mm

Solution

Q5. An iron bar of length l cm and cross section A cm² is pulled by a force F dynes from the ends so as to produce an elongation l cm. Which of the following statements is correct?

• Elongation is inversely proportional to length.
• Elongation is inversely proportional to area of cross-section A.
• Elongation is directly proportional to area of cross-section A.
• Elongation is directly proportional to Young's modulus.

Solution

F = YAl / LOr, l = F L / Y AFrom above equation, elongation is inversely proportional to area of cross-section A.

Q6. The following four wires are made of the same material. Which of these will have the largest extension when same tension is applied?

• length 50 cm and diameter 0.5 mm
• length 100 cm and diameter 1 mm
• length 200 cm and diameter 2 mm
• length 300 cm and diameter 3 mm

Solution

Q7. Breaking stress is ______ for a material, but breaking force ____ and depends on _____________.

• fixed, varies, area of cross section
• variable, fixed ,area of cross section
• fixed, varies, material
• varies, fixed, material

Solution

Breaking stress is fixed for a material, but breaking force varies and depends on area of cross section.

Q8. A solid cylinder can be subjected to

• tensile stress
• compressive stress
• shearing stress
• all the above

Solution

A solid body can experience all types of stresses depending upon the direction the applied force.

Q9. Which of the following factors can bring about a change in the elastic properties of a material?

• Change in temperature
• Presence of impurities
• Both (i) and (ii)
• None of the above

Solution

Change in temperature and presence of impurities changes the elastic properties of body.

Q10. Which of the following forces is responsible for elastic behavior of a substance?

• Deforming force
• Restoring force
• Tangential force
• Shear force

Solution

Restoring force is responsible for the elastic behavior of substance.

Q11. If fifty pounds of force stretches a spring by five inches, how much will the spring be stretched by a force of 120 pounds?

• 10 inch
• 12 inch
• 13 inch
• 15 inch

Solution

Q12. In Hooke's law, the constant of proportionality signifies

• modulus of stress
• modulus of strain
• elasticity of wire
• modulus of elasticity

Solution

Hooke's law states, that stress is proportional to strain Stress α strain Stress = modulus of elasticity x strain

Q13. Materials that show very small plastic range beyond elastic limit are called

• Ductile materials
• Brittle materials
• Elastic materials
• Elastomers

Solution

Brittle materials have shorter plastic region, i.e., the proportional and fracture points are close.

Q14. Which of the following statements is true?

• Liquids have zero value of modulus of rigidity.
• Gases have zero value of modulus of rigidity.
• Both (i) and (ii)
• None of the above

Solution

This is because liquids and gases do not have shape of themselves.

Q15. Tissue of aorta blood vessel is an example of

• perfectly elastic body
• perfectly plastic body
• elastomer
• state of permanant deformation

Solution

Substances like aorta tissue can be stretched to cause large strains. Hence they are known as elastomers.

Q16. The volume of a spherical body is decreased by 10^-3% when it is subjected to pressure of 40 atmospheres. Find the bulk modulus of body. (1 atm = 1.01 x 10³ N/m²).

• 4.04 x 10⁶ N/m²
• 4.04 x 10² N/m²
• 4.04 x 10³ N/m²
• 4.04 x 10¹¹ N/m²

Solution

Q17. When a elastic material with Young's modulus Y is subjected to a stretching stress S. The elastic energy stored per unit volume of the material is

• YS/2
• S²Y/2
• S²/2Y
• S/2Y

Solution

The elastic energy stored per unit volume of the material is

Q18. The final point on the stress strain graph is called

• Yield point
• Elastic limit
• Fracture point
• Proportional limit

Solution

The final point on the stress-strain graph indicates the Fracture point.

Q19. The stress which is set up in the body due to increase in its dimensions is called

• Normal stress
• Tangential stress
• volumetric stress
• Tensile stress

Solution

The stress which is set up in the body due to increase in its dimensions is called tensile stress.

Q20. A solid sphere placed in a fluid under high pressure experiences force

• in downward direction only
• sideways only
• in all the directions
• upwards only

Solution

A solid sphere immersed in a liquid will experience compressive force perpendicular to all the points on the surface. Hence, the sphere is said to be in hydraulic compression.

Q21. For elastomers, stress and strain variation is _________ within elastic limit.

• a straight line
• an elliptical
• not a straight line
• none of the above

Solution

It is not a straight line. Elastomers do not obey Hooke's law.

Q22. Dimensional formula of stress is same as that of

• impulse
• strain
• force
• pressure

Solution

Both stress & pressure are defined as force per unit area

Q23. Two wires P and Q of same length and material but radii in the ratio 2 : 1 are suspended from a rigid support. Find the ratio of strain produced in the wires when both are under same force.

• 1 : 2
• 2 : 1
• 1 : 4
• 4 : 1

Solution

Q24. A force of 600 newtons will compress a spring 0.5 metres. What is the spring constant of the spring?

• 300
• 1200
• 100
• 1000

Solution

Q25. What type of stress is produced in a body when the deforming force produces sheer strain?

• Normal stress
• Tangential stress
• Longitudinal stress
• shear stress

Solution

Tangential stress is produced in a body when the deforming force produces sheer strain.

Q26. Putty or mud is an example of

• plastic material
• elastic material
• elastomers
• semi elastic

Solution

Since mud or putty have no gross tendency to regain their previous shape & they get permanently deformed, they are close to ideal plastics.

Q27. The area occupied below the stress-strain graph and above strain axis gives the value of

• work done in producing extension
• energy density of the material
• energy stored in the material
• Restoring force.

Solution

The area occupied below the stress-strain graph and above strain axis gives the value of energy density of the material.

Q28. How does the modulus of elasticity change with temperature?

• It increases with increase in temperature
• It decreases with increase in temperature
• It sometimes increases, sometimes decreases with increase in temperature
• It does not depend on temperature

Solution

The modulus of elasticity decreases with increase in temperature.

Q29. What is the relation between compressibility and Bulk modulus?

• Compressibility is the reciprocal of bulk modulus
• Compressibility is the reciprocal of square root of bulk modulus
• Compressibility is directly proportional to bulk modulus
• Compressibility is directly proportional to square of bulk modulus

Solution

Compressibility is the reciprocal of bulk modulus.

Q30. Tangential force produces

• tensile strain
• compressive strain
• shear strain
• random strain