Q121 / 160 · AP EAMCET 2018 (23 Apr Shift 1) · Physics

Assertion (A) Energy per unit volume and angular momentum can be added dimensionally. Reason (R) Physical quantities having same dimensions can be added or subtracted.

  • A
    Both (A) and (R) are true and (R) is the correct explanation of (A)
  • B
    Both (A) and (R) are true but (R) is not the correct explanation of (A)
  • C
    (A) is true but (R) is false
  • Correct answer
    D
    (A) is false but (R) is true

Solution

The units of energy per unit volume is $\mathrm{J} / \mathrm{m}^3$ or $\mathrm{kg} / \mathrm{m}-\mathrm{s}^2$ and that for angular momentum is $\mathrm{kg}-\mathrm{m}^2 / \mathrm{s}$. Since, they are not dimensionally equal, they cannot be added, so the Assertion (A) is false. Only those physical quantities that have same dimensions can be added or subtracted, so Reason (R) is true. Hence, the correct option is $(\mathrm{d})$.

Hence, the correct answer is option: 'D'.

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