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Consider two physical quantities A and B related to each other as E = fracB - x^2At where E, x and t have dimensions of energy, length and time respectively. The dimension of AB is

Solution & Explanation

### Related Formula By the Principle of Homogeneity, terms added or subtracted must have the same dimensions: [B] = [x^2] ### Core Logic Known dimensional formulas: Length x to [L] Energy E to [ML^2T^-2] Time t to [T] ### Step 1: Dimension of B Since x^2 is subtracted from B: [B] = [x^2] = [L^2] ### Step 2: Dimension of A From the equation E = fracB - x^2At: [A] = frac[B - x^2][E][t] [A] = frac[L^2][ML^2T^-2][T] = frac[L^2][ML^2T^-1] [A] = [M^-1T^1] ### Step 3: Dimension of AB [AB] = [A] times [B] [AB] = [M^-1T^1] times [L^2] [AB] = [L^2 M^-1 T^1] ### Pattern Recognition Identify sums/differences first to instantly isolate B. Once [B] is fixed, the entire numerator is just L^2. Swap out variables to isolate [A]. Combining is just standard exponent addition. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Physics: Units and Measurements

Reference Study Guides

More Units and Measurements Previous-Year Questions — Page 8

Q41 jee_main_2024_31_jan_morning Dimensional Analysis
A force is represented by F = ax^2 + bt^1/2 Where x = distance and t = time. The dimensions of b^2 / a are:
  • A. [ML^3T^-3]
  • B. [MLT^-2]
  • C. [ML^-1T^-1]
  • D. [ML^2T^-3]

Solution

### Related Formula textPrinciple of Homogeneity: [F] = [ax^2] = [bt^1/2] ### Core Logic By the principle of dimensional homogeneity, each additive term must have the same dimension as the left hand side. Dimension of force F = [M L T^-2]. For the term ax^2: [a] = frac[F][x^2] = frac[M L T^-2][L^2] = [M L^-1 T^-2] For the term bt^1/2: [b] = frac[F][t^1/2] = frac[M L T^-2][T^1/2] = [M L T^-5/2] ### Step 2: Computing Required Ratio We need the dimension of fracb^2a: left[ fracb^2a right] = frac[M L T^-5/2]^2[M L^-1 T^-2] left[ fracb^2a right] = frac[M^2 L^2 T^-5][M L^-1 T^-2] left[ fracb^2a right] = [M^2-1 L^2 - (-1) T^-5 - (-2)] left[ fracb^2a right] = [M L^3 T^-3] ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Physics: Units And Measurements

More Units and Measurements Questions — jee_main_2024_31_jan_evening

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