Dimensions of universal gravitational constant (G) in terms of Planck's constant (h), distance (L), mass (M) and time (T) are .
- [ hTLM-2 ]
- [ hT-1LM-2 ]
- [ hTL2M-2 ]
- [ h-1T-1LM-2 ]
Answer
(2) [ hT-1LM-2 ]
Solution
[G] = [M-1L3T-2] ∵ F = Gm1m2r2
[h] = [ML2T-1] ∵ E = h
Let [G] = [haTbLcMd] = [Ma+dL2a+cT-a+b]
Comparing powers:
M: a + d = -1, L: 2a + c = 3, T: -a + b = -2
Four unknowns, three equations ⇒ check the options: every option has M-2, so d = -2
⇒ a = 1, c = 3 - 2 = 1, b = -2 + 1 = -1
∴ [G] = [hT-1LM-2]
Check: [ML2T-1][T-1][L][M-2] = [M-1L3T-2] ✓
Answer: (2)