Physics · Units, Dimensions & Error Analysis

JEE Main 2025 — 29 January, Evening Shift — Question 39

A physical quantity Q is related to four observables a,b,c,da, b, c, d as follows : Q=a4cdQ=\frac{a^{4}}{c d} where, a=(60±3)Pa;b=(20±0.1)m;\mathrm{a}=(60 \pm 3) \mathrm{Pa} ; \mathrm{b}=(20 \pm 0.1) \mathrm{m} ; c=(40±0.2)Nsm−2c=(40 \pm 0.2) \mathrm{Nsm}^{-2} and d=(50±0.1)m\mathrm{d}=(50 \pm 0.1) \mathrm{m}, then the percentage error in QQ is x1000\frac{x}{1000}, where x=\mathrm{x}= \qquad .

Answer: 77

Numerical answer — enter this value.

Step-by-step solution

Q=ab4 cd\mathrm{Q}=\frac{\mathrm{ab}^{4}}{\mathrm{~cd}}

⇒ΔQQ×100=[Δaa+4Δ b b+Δcc+Δdd]×100\Rightarrow \frac{\Delta \mathrm{Q}}{\mathrm{Q}} \times 100=\left[\frac{\Delta \mathrm{a}}{\mathrm{a}}+4 \frac{\Delta \mathrm{~b}}{\mathrm{~b}}+\frac{\Delta \mathrm{c}}{\mathrm{c}}+\frac{\Delta \mathrm{d}}{\mathrm{d}}\right] \times 100

⇒x1000=[360+4(0.120)+(0.240)+0.150]×100\Rightarrow \frac{\mathrm{x}}{1000}=\left[\frac{3}{60}+4\left(\frac{0.1}{20}\right)+\left(\frac{0.2}{40}\right)+\frac{0.1}{50}\right] \times 100

⇒x=7700\Rightarrow \mathrm{x}=7700

Answer key and solution verified before publishing.

Practise Units, Dimensions & Error Analysis

Start with this question, then two more from the same chapter — with a tutor that explains every step. Free.

Exam
JEE Main 2025
Subject
Physics
Chapter
Units, Dimensions & Error Analysis
Topic
Significant Figures and Error Analysis