JEE Mains · Physics · STD 11- Mechanical properties of solids
- JEE Mains 2026
- Easy
- MCQ
The speed of a longitudinal wave in a metallic bar is \(400~m/s.\) If the density and Young's modulus of the bar material are increased by 0.5% and 1% respectively then the speed of the wave is changed approximately to ___________ \(m / s\).
Pick an option to check your answer.
Answer & Solution
Correct Answer
(D) 401
Step-by-step Solution
Detailed explanation
\(V_{sound}=\sqrt{\frac{Y}{\rho}}\)
\(\frac{\Delta V}{V}\times100=\frac{1}{2}(\frac{\Delta Y}{Y}\times100)-\frac{1}{2}(\frac{\Delta\rho}{\rho}\times100)\)
\(=\frac{1}{2}\times1-\frac{1}{2}\times0.5\)
\(\frac{\Delta V}{V}\times100=\frac{1}{4}\)
\(\Delta V=\frac{1}{4}\times\frac{V}{100}\)
\(\Delta V=1m/s\)
\(V_{final}=400+1=401~m/s\)
\(\frac{\Delta V}{V}\times100=\frac{1}{2}(\frac{\Delta Y}{Y}\times100)-\frac{1}{2}(\frac{\Delta\rho}{\rho}\times100)\)
\(=\frac{1}{2}\times1-\frac{1}{2}\times0.5\)
\(\frac{\Delta V}{V}\times100=\frac{1}{4}\)
\(\Delta V=\frac{1}{4}\times\frac{V}{100}\)
\(\Delta V=1m/s\)
\(V_{final}=400+1=401~m/s\)
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