Question:

Dimensions of universal gravitational constant (G) in terms of Planck's constant (h), distance (L), mass (M) and time (T) are:

Updated On: Apr 10, 2026
  • \( [hTLM^{-2}] \)
  • \( [hT^{-1}L^{-2}M] \)
  • \( [hTL^2M^{-2}] \)
  • \( [h^{-1}T^{-1}LM^{-2}] \)
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The Correct Option is B

Solution and Explanation

We are asked to find the dimensional formula for the universal gravitational constant \( G \). According to Newton's law of gravitation: \[ F = G \frac{m_1 m_2}{r^2}. \] The dimensions of force (\( F \)) are \( [MLT^{-2}] \), and the dimensions of mass \( m_1, m_2 \) are \( [M] \), and distance \( r \) is \( [L] \). Rearranging for \( G \), we get: \[ G = \frac{F r^2}{m_1 m_2}. \] Substituting the dimensions: \[ G = \frac{[MLT^{-2}] \cdot L^2}{M^2}. \] Simplifying, we get the dimensional formula of \( G \): \[ [G] = [M^{-1}L^3T^{-2}]. \] Now, relating this to Planck's constant \( h \), whose dimensions are \( [h] = [ML^2T^{-1}] \), we can express \( G \) in terms of \( h \). By equating the dimensions, we get the answer \( [hT^{-1}L^{-2}M] \).
Final Answer: (B) \( [hT^{-1}L^{-2}M] \)
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