Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NEET
Exam
NEET
Subject
Physics
Chapter
Units and Dimensions

NEET · Physics · Units and Dimensions

The time period T of an oscillating liquid drop is assumed to...

The time period TT of an oscillating liquid drop is assumed to depend on its radius RR, density ρ\rho, and surface tension SS. If the percentage errors in the measurement of RR, ρ\rho, and SS are 2%2\%, 1%1\%, and 3%3\% respectively, what is the maximum percentage error in the calculated value of TT?

Options

  1. A2%2\%
  2. B5%5\%
  3. C6%6\%
  4. D10%10\%

Correct answer

B. 5%5\%

Step-by-step solution

Let T=kSαρβRγT = k S^\alpha \rho^\beta R^\gamma, where kk is a dimensionless constant.

Writing the dimensions of each quantity:
[T]=[M0L0T1][T] = [M^0 L^0 T^1]
[S]=[M1L0T−2][S] = [M^1 L^0 T^{-2}]
[ρ]=[M1L−3T0][\rho] = [M^1 L^{-3} T^0]
[R]=[M0L1T0][R] = [M^0 L^1 T^0]

Substituting these into the equation:
[M0L0T1]=[MT−2]α[ML−3]β[L]γ[M^0 L^0 T^1] = [M T^{-2}]^\alpha [M L^{-3}]^\beta [L]^\gamma
[M0L0T1]=[Mα+βL−3β+γT−2α][M^0 L^0 T^1] = [M^{\alpha+\beta} L^{-3\beta+\gamma} T^{-2\alpha}]

Equating the powers of M,LM, L, and TT on both sides:
For TT: −2α=1⇒α=−12-2\alpha = 1 \Rightarrow \alpha = -\dfrac{1}{2}
For MM: α+β=0⇒β=−α=12\alpha + \beta = 0 \Rightarrow \beta = -\alpha = \dfrac{1}{2}
For LL: −3β+γ=0⇒γ=3β=32-3\beta + \gamma = 0 \Rightarrow \gamma = 3\beta = \dfrac{3}{2}

Therefore, the relation is T∝S−1/2ρ1/2R3/2T \propto S^{-1/2} \rho^{1/2} R^{3/2}.

The maximum percentage error in TT is given by:
ΔTT×100=∣−12∣(ΔSS×100)+∣12∣(Δρρ×100)+∣32∣(ΔRR×100)\dfrac{\Delta T}{T} \times 100 = \left|-\dfrac{1}{2}\right| \left(\dfrac{\Delta S}{S} \times 100\right) + \left|\dfrac{1}{2}\right| \left(\dfrac{\Delta \rho}{\rho} \times 100\right) + \left|\dfrac{3}{2}\right| \left(\dfrac{\Delta R}{R} \times 100\right)

Substituting the given percentage errors:
% error in T=12(3%)+12(1%)+32(2%)\% \text{ error in } T = \dfrac{1}{2}(3\%) + \dfrac{1}{2}(1\%) + \dfrac{3}{2}(2\%)
=1.5%+0.5%+3%=5%= 1.5\% + 0.5\% + 3\% = 5\%.

Answer: 5%5\%
Practice Units and Dimensions on Quantrex Academy →

More from Units and Dimensions

If the errors involved in the measurement of a side and the mass of a cube are 2\% and… MHT CET Medical 2026If the mass of the object is measured as m = (7 ∓ 0.14) kg and the density is measured as… MHT CET Medical 2026Consider that σ_s , k_B , b represent Stefan-Boltzmann constant, Boltzmann constant and… NEET 2026The speed of light in vacuum is taken as unity. If light takes 6 min 40 s to reach the… NEET 2026Each side of a metallic cube of mass 5.580 kg is measured to be 9.0 cm. Keeping the… NEET 2026A physical quantity P is related to four observations a, b, c and d as follows : P=a^3… NEET 2025A balloon is made of a material of surface tension S and its inflation outlet (from where… NEET 2025The quantities which have the same dimensions as those of solid angle are: NEET 2024 Full Units and Dimensions list All NEET PYQs