# Class 11th Physics – 9 Mechanical properties of solids MCQs

#### Which of the following is close to ideal plastic?

Correct! Wrong!

Among the given material putty is the material that is close to ideal plastic.

#### The slope of stress (plotted on Y axis) and strain (plotted on X axis) gives the ____ of the material under observation.

Correct! Wrong!

The slope of stress (plotted on Y axis) and strain (plotted on X axis) gives the modulus of elasticity of the material under observation.

#### If 6 cm cube has its upper face displaced by 0.2 cm by a tangential force of 8 N, then the shearing strain will be ____.

Correct! Wrong!

L = 6 cm = 6 × 10-2 m, ΔL = 0.2 cm = 0.2 ×10-2 m, F = 8 N
Shearing strain = ΔL/L = 0. 2/6 = 0. 03

#### Which of the following should be considered while selecting a material for the rope of a crane?

Correct! Wrong!

While selecting a material for the rope of a crane, we should consider the elastic limit and the Young’s modulus of the material. This gives an idea of the maximum load that can be lifted using the rope of given thickness made of the material.

#### The relation between stress and strain of a deformed body depends on ____.

Correct! Wrong!

The relation between stress and strain of a deformed body depends on the material of the body.

#### The bulk modulus of a perfectly rigid body is equal to ____.

Correct! Wrong!

For a perfectly rigid body ΔV = 0 Therefore, Bulk modulus B = - (∆ρ)/(∆V/V) = ∞

#### The force which changes or tends to change the shape and size of an object is ____.

Correct! Wrong!

The force which changes the shape and size of an object is called deformation force.

#### If forces are applied on all sides of a body uniformly; the deformation produced in the body is called ____.

Correct! Wrong!

If forces are applied on all sides of a body uniformly, the volume of the body changes and hence, deformation produced in the body is called bulk deformation.

#### The straight line portion of the stress strain curve of a body indicates the ___ of the body.

Correct! Wrong!

The straight line portion of the stress strain curve of a body indicates the elastic behaviour of the body. In this region, the stress is directly proportional to the strain.

#### Statement (i): In solids, the molecules occupy fixed positions.

Correct! Wrong!

In solids, the molecules occupy fixed positions and their relative positions are also fixed.

Correct! Wrong!

Crane ropes are made of several strands instead of one. This increases the strength of the rope.

#### A steel wire is stretched by 1 kg weight. If the radius of the wire is doubled, then its Young's modulus will be ____.

Correct! Wrong!

Young's modulus is defined for a solid material when we apply normal stress. It is a property of the material. Hence, it is constant and does not change.

#### The depth to which a rubber ball should be taken below the surface of a lake containing water so as to have a decrease in volume of 0.1% is ____.

Correct! Wrong!

Here, B = PV/ΔV = hρgV/ΔV
∴ 9. 8×108 = h×1000×9.89×1000/1
h = 100 m.

#### The branch of science which deals with the strength of buildings and constructions is ____.

Correct! Wrong!

The branch of science which deals with the strength of buildings and constructions is structural engineering.

#### The SI unit of stress is ____.

Correct! Wrong!

Stress is the ratio of force per unit area. Hence, it is measured in SI system in N/m2

#### If there is an increase in the length of the body in the direction of force applied, the stress set up is called ____.

Correct! Wrong!

If there is an increase in the length of the body in the direction of force applied; the stress is called tensile stress.

#### In a stress strain curve of a body, the fracture point indicates the stress at which the body ____.

Correct! Wrong!

In a stress strain curve of a body, the fracture point indicates the stress at which the body breaks under the stress.

#### Hooke's law essentially defines ____

Correct! Wrong!

Hooke's law is defined within the elastic limit, according to which Stress ∝ Strain.

#### The shear modulus of elasticity of a liquid is ____.

Correct! Wrong!

Shear modulus of elasticity of a liquid is zero because liquid does not resist change in its shape.

#### Young's modulus is defined as ____.

Correct! Wrong!

Young's modulus of elasticity (Y) is defined as the ratio of normal stress to the longitudinal strain, within elastic limit. ∴Y = normal stress / longitudinal strain = σ/ε

#### Beams used in construction of bridges, as supports etc have a cross section that resembles an alphabet. Which of the following is the alphabet?

Correct! Wrong!

Beams used in construction of bridges, as supports etc have a cross section that resembles the alphabet “I”. This gives the structure more strength.

#### The ratio of radii two wires of same material is 4 : 2. If these wires are stretched by equal force, then the ratio of stresses produced in them will be ____.

Correct! Wrong!

r1: r2 = 4: 2, F1 = F2 = F
Stress = force/area = F/Πr2
∴S∝1/r2
So, S1/ S2 = r22/r12 = (2/4)2= 4/16 = ¼

#### Hooke's law states that ____.

Correct! Wrong!

The modified form of Hooke's law states that "within elastic limit, the stress developed is directly proportional to the strain produced in a body."
Stress ∝ Strain
Stress = E × Strain
Where E is a constant, known as Modulus of elasticity of the material of the body.

#### Shearing strain is expressed by ____.

Correct! Wrong!

Shearing strain is defined as an angle in radian through which a plane perpendicular to the fixed surface of the cubical body gets turned under the tangential force. Shearing strain is expressed by angle of shear.

#### The MKS unit of Young's modulus is ____

Correct! Wrong!

The unit of Young's modulus of elasticity in MKS (SI) is N m-2 or pascal (denoted by pa).

#### The force that is responsible to bring back the shape and size of a body to its original once the deformation force is relieved is called ____.

Correct! Wrong!

The force that is responsible to bring back the shape and size of a body to its original once the deformation force is relieved is called the restoring force.

#### Generally, Young's modulus of elasticity ____ .

Correct! Wrong!

We know that inter-atomic binding energy decreases with temperature. So, more strain is produced at high temperature. Therefore, Y decreases with increase in temperature.

#### When the shape and size of a body does not change on application of force, the body is referred to as ____.

Correct! Wrong!

When the shape and size of a body does not change on application of force, the body is referred to as a rigid body.

#### When the length of a body is affected the most under the action of a deformation force, the deformation is called ____.

Correct! Wrong!

When the length of a body is affected the most under the action of a deformation force, the deformation is called longitudinal deformation.

#### Which of the following is recommended for rope in a crane?

Correct! Wrong!

A number of thin wires braided together are recommended for rope in a crane as it provides more strength compared to a single wire of larger area of cross section of the same material. Also it facilitates the manufacturing.

Class 11th Physics - 9 Mechanical properties of solids MCQs
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