Laws In Physics

Concept: Work done:

Step 1: Check statements.

• Work depends on force and displacement, not time

Step 2: Conclusion.
Statement (E) is incorrect.

Concept:
• Polar vs non-polar molecules

Step 1: Check statements
(A) Not always true (air is mixture)
(B) False (they do not coincide in polar molecules)
(C) False (water is polar)
(D) False (dielectrics are insulators)
(E) True Final Conclusion:
Option (E)

Step 1: Understanding the Concept:
The mechanical properties of materials heavily dictate how they respond to applied forces, stresses, and pressures.
We must systematically verify the validity of each provided statement based on fundamental definitions.
Step 2: Key Formula or Approach:
The approach involves fact-checking each distinct statement against standard physics definitions for Stress, Young's Modulus, and Bulk Modulus (Compressibility).
Step 3: Detailed Explanation:
Statement (A) says "Stress is not a vector quantity." This is entirely correct, as stress is mathematically defined as a second-order tensor, not a simple vector.
Statement (B) says "Young's modulus is only applicable for solids." This is correct because Young's modulus measures resistance to changes in linear length, and only solid bodies have defined independent lengths that can support tension and compression.
Statement (C) says "Compressibility is applicable for solids, liquids and gases." This is correct since compressibility is the reciprocal of the bulk modulus, and all states of matter can undergo volumetric compression under uniform pressure.
Statement (D) says "Young's modulus is greater for elastomers than metal." This statement is distinctly false.
Young's modulus represents stiffness. Metals are incredibly stiff and require massive forces to stretch slightly, resulting in a very high Young's modulus. Elastomers (like rubber) stretch very easily with little force, yielding a very small Young's modulus.
Step 4: Final Answer:
The demonstrably incorrect statement is (D).