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 the average strain produced in the direction of the force?

(A)

^{F}/_{4SE}

(B)

Zero

(C)

^{F}/_{SE}

(D)

^{F}/_{2SE}

Question-2

A 5 m long steel wire is suspended from the ceiling of a room. A sphere of mass 25 kg and 10 cm radius is attached to another end of the wire. The height of the ceiling is 5.21 m. When the sphere is made to oscillate as a pendulum, then its lowest point just touches the floor. The velocity of the sphere at the lowest point will be :

(Given : Y = 2 x 10^{11}N/m^{2}, radius of wire = 0.05 cm)

(A)

3.71 m/s

(B)

3.71 cm/s

(C)

37.1 cm/s

(D)

37.1 m/s

Question-3

A thick rope of density 'ρ' and length 'L' is hung from a rigid support. The Young's modulus of the material of rope is 'Y'. The increase in length of the rope due to its own weight is :

(A)

1/4 ρgL^{2}/Y

(B)

1/2 ρgL^{2}/Y

(C)

ρ gL^{2}/Y

(D)

ρ gL/Y

Question-4

A steel wire of uniform cross-section of 2 mm^{2} is heated upto 50^{o}C and clamped rigidly at two ends. If the temperature of wire falls to 30^{o}C then change in tension in the wire will be :

(Given : Coefficient of linear expansion of steel is 1.1 x 10^{-5°}C and Young's modulus of elasticity of steel is 2 x 10^{11}N/m^{2})

(A)

22 N

(B)

44 N

(C)

88 N

(D)

132 N

Question-5

The length of an iron wire is L and area of cross-section is A. The increase in length is l on applying the force F on its two ends. Which of the statement is correct ?

(A)

Increase in length is inversely proportional to A

(B)

Increase in length is proportional to Young's modulus

(C)

Increase in length is inversely proportional to its length L

(D)

Increase in length is proportional to area of cross-section A

Question-6

An aluminium rod of Young's modulus 7.0 x 10^{9} N/m^{2} has a breaking strain of 0.2%. The minimum cross-sectional area of the rod in m^{2} in order to support a load of 10^{4} newton is :

(A)

1.0 x 10^{-2}

(B)

1.0 x 10^{-3}

(C)

1.4 x 10^{-2}

(D)

7.1 x 10^{-4}

Question-7

Young's modulus of the material of a wire of length L and radius r is Y N/m^{2}. If the length is reduced to ^{L}/_{2} and radius to ^{r}/_{2}, the Young's modulus will be :

(A)

Y/4

(B)

Y/2

(C)

Y

(D)

2Y

Question-8

The magnitude of the force developed by raising the temperature from 0^{o}C to 100^{o}C of the iron bar 1.00 m long and 1 cm^{2} cross-section when it is held so that it is not permitted to expand or bend is :

(Given : α = 10^{-5} /^{o}C and Y = 10^{11} N/m^{2})

(A)

10^{3 }N

(B)

10^{4 }N

(C)

10^{5 }N

(D)

10^{9 }N

Question-9

The upper end of a wire, 1 m long and 4 mm radius, is clamped. The lower end is twisted by an angle of 30^{o}. The angle of shear at the surface is :

(A)

12^{o}

(B)

1.2^{o}

(C)

0.12^{o}

(D)

0.012^{o}

Question-10

For the same cross-sectional area and for a given load, teh ratio of depressions for the beam of a square cross-section and circular cross-section is :

(A)

3 : π

(B)

π : 3

(C)

1 : 1

(D)

1 : π

Your Score 0/10

Click here to see your answersheet and detailed track records.