Question 1

Given below are two statements: 

Statement (I) : Planck's constant and angular momentum have the same dimensions.

Statement (II) : Linear momentum and moment of force have the same dimensions. In light of the above statements, choose the correct answer from the options given below :

We need to check the dimensional correctness of both statements.

Statement (I): Planck's constant and angular momentum have the same dimensions.

Planck's constant $$h$$ has the relation $$E = h\nu$$, so:

$$[h] = \frac{[E]}{[\nu]} = \frac{ML^2T^{-2}}{T^{-1}} = ML^2T^{-1}$$

Angular momentum $$L = mvr$$, so:

$$[L] = M \cdot LT^{-1} \cdot L = ML^2T^{-1}$$

Both have the same dimensions $$ML^2T^{-1}$$. Statement (I) is true.

Statement (II): Linear momentum and moment of force have the same dimensions.

Linear momentum $$p = mv$$:

$$[p] = MLT^{-1}$$

Moment of force (torque) $$\tau = r \times F$$:

$$[\tau] = L \cdot MLT^{-2} = ML^2T^{-2}$$

The dimensions are different: $$MLT^{-1} \neq ML^2T^{-2}$$. Statement (II) is false.

Therefore, Statement I is true but Statement II is false.

The correct answer is Option A.

Create a FREE account and get:

  • Free JEE Mains Previous Papers PDF
  • Take JEE Mains paper tests