BITSAT Physics Mechanical Properties Of Solids MCQs

Question: Two wires are made of the same material and have the same volume. However wire 1 has cross-sectional area A and wire 2 has crosssectional area 3A. If the length of wire 1 increases by Δx on applying force F, how much force is needed to stretch wire 2 by the same amount?

• a) 4 F
• b) 6 F
• c) 9 F
• d) F

Answer: 9 F

Question: A steel wire is stretched by 1 kg wt. If the radius of the wire is doubled, its Young’s modulus will

• a) Remain unchanged
• b) Become half
• c) Become double
• d) Become four times

Answer: Remain unchanged

Question: A cube is subjected to a uniform volume compression. If the side of the cube decreases by 2% the bulk strain is

• a) 0.02
• b) 0.03
• c) 0.04
• d) 0.06

Answer: 0.06

Question: The Young’s modulus of a perfectly rigid body is

• a) Unity
• b) Zero
• c) Infinity
• d) Some finite non-zero constant

Answer: Infinity

Question:  An iron rod of length 2m and cross-sectional area of 50 mm² stretched by 0.5 mm, when a mass of 250 kg is hung from its lower end. Young’s modulus of iron rod is

• a) 19.6 × 1020 N/m² 
• b) 19.6 × 1018 N/m²
• c) 19.6 × 1010 N/m²
• d) 19.6 × 1015 N/m²

Answer: 19.6 × 1010 N/m²

Question: The upper end of a wire of diameter 12mm and length 1m is clamped and its other end is twisted through an angle of 30°. The angle of shear is

• a) 18°
• b) 0.18°
• c) 36°
• d) 0.36°

Answer: 0.18°

Question: A metallic rod breaks when strain produced is 0.2%. The Young’s modulus of the material of the rod is 7 × 10⁹ N/m². What should be its area of cross-section to support a load of 10⁴ N ?

• a) 7.1 × 10^–8 m²
• b) 7.1 × 10^–6 m²
• c) 7.1 × 10^–4 m²
• d) 7.1 × 10^–2 m²

Answer: 7.1 × 10^–4 m²

Question: 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

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: 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) r g L²/Y
• b) (1/2) r g L²/Y
• c) r g L²/Y
• d) r g L/Y

Answer: (1/2) r g L²/Y

Question: If the ratio of radii of two wires of same material is 2 : 1 and ratio of their lengths is 4 : 1, then the ratio of the normal forces that will produce the same extension in the length of two wires is

• a) 2 : 1
• b) 4 : 1
• c) 1 : 4
• d) 1 : 1

Answer: 1 : 1