KCET · Maths · Area Under Curves
If the area between \(y=m x^{2}\) and \(x=m y^{2}(m>0)\) is \(1 / 4 \mathrm{sq}\) units, then the value of \(m\) is
- A \(\pm 3 \sqrt{2}\)
- B \(\pm \frac{2}{\sqrt{3}}\)
- C \(\sqrt{2}\)
- D \(\sqrt{3}\)
Answer & Solution
Correct Answer
(B) \(\pm \frac{2}{\sqrt{3}}\)
Step-by-step Solution
Detailed explanation
Given curves; \(y=m x^{2}\) and \(y^{2} m=x ; m>0\)
Intersection point of both curves;
\(x=m\left(m x^{2}\right)^{2}=m^{3} x^{4}\)
\(\Rightarrow \quad m^{3} x^{4}-x=0\)
\[
\begin{array}{cc}
\Rightarrow & x\left(m^{3} x^{3}-1\right)=0 \\
\Rightarrow & x(m x-1)\left(m^{2} x^{2}+1+m x\right)=0 \\
\Rightarrow & x=0, x=1 / m \text { and } y=0, y=1 / m
\end{array}
\]
We take only the points
\[
=(0,0) \text { and }(1 / m, 1 / m)
\]
Now, the area of the curve
\[
\begin{aligned}
&=\int_{0}^{1 / m}\left(\sqrt{\frac{x}{m}}-m x^{2}\right) d x \\
\text { Given, } \quad \frac{1}{4} &=\left[\frac{2}{3 \sqrt{m}} \cdot x^{3 / 2}-m \cdot \frac{x^{3}}{3}\right]_{0}^{1 / m} \\
\Rightarrow \quad \frac{1}{4} &=\left[\frac{2}{3 \sqrt{m}} \cdot \frac{1}{m^{3 / 2}}-\frac{m}{3} \cdot \frac{1}{m_{3}}\right] \\
\Rightarrow \quad \frac{1}{4} &=\left\{\frac{2}{3 m^{2}}-\frac{1}{3 m^{2}}\right\} \\
\Rightarrow \quad \frac{1}{4} &=\frac{1}{3 m^{2}} \Rightarrow m^{2}=\frac{4}{3} \\
\therefore \quad m=\pm \frac{2}{\sqrt{3}}
\end{aligned}
\]
Intersection point of both curves;
\(x=m\left(m x^{2}\right)^{2}=m^{3} x^{4}\)
\(\Rightarrow \quad m^{3} x^{4}-x=0\)
\[
\begin{array}{cc}
\Rightarrow & x\left(m^{3} x^{3}-1\right)=0 \\
\Rightarrow & x(m x-1)\left(m^{2} x^{2}+1+m x\right)=0 \\
\Rightarrow & x=0, x=1 / m \text { and } y=0, y=1 / m
\end{array}
\]
We take only the points
\[
=(0,0) \text { and }(1 / m, 1 / m)
\]
Now, the area of the curve
\[
\begin{aligned}
&=\int_{0}^{1 / m}\left(\sqrt{\frac{x}{m}}-m x^{2}\right) d x \\
\text { Given, } \quad \frac{1}{4} &=\left[\frac{2}{3 \sqrt{m}} \cdot x^{3 / 2}-m \cdot \frac{x^{3}}{3}\right]_{0}^{1 / m} \\
\Rightarrow \quad \frac{1}{4} &=\left[\frac{2}{3 \sqrt{m}} \cdot \frac{1}{m^{3 / 2}}-\frac{m}{3} \cdot \frac{1}{m_{3}}\right] \\
\Rightarrow \quad \frac{1}{4} &=\left\{\frac{2}{3 m^{2}}-\frac{1}{3 m^{2}}\right\} \\
\Rightarrow \quad \frac{1}{4} &=\frac{1}{3 m^{2}} \Rightarrow m^{2}=\frac{4}{3} \\
\therefore \quad m=\pm \frac{2}{\sqrt{3}}
\end{aligned}
\]
See the Complete Solution
Get step-by-step explanations for this and 2.5 Lakh+ more JEE, NEET & CET questions.
- Unlock all solutions
- Practice the full chapter
- Track accuracy across PYQs
4.8 rated on Google Play · 14,000+ reviews
More questions from Maths
- The value of \(\sin ^{2} 51^{\circ}+\sin ^{2} 39^{\circ}\) isKCET 2020 Medium
- The angle between the line \(x+y=3\) and the line joining the points \((1,1)\) and \((-3,4)\) isKCET 2024 Easy
- The constant term of the polynomial \(\left|\begin{array}{ccc}x+3 & x & x+2 \\ x & x+1 & x-1 \\ x+2 & 2 x & 3 x+1\end{array}\right|\) isKCET 2010 Medium
- The length of the chord of the circle \(x^{2}+y^{2}+3 x+2 y-8=0\) intercepted by the \(y\)-axis isKCET 2013 Easy
- If \(1, \omega, \omega^{2}\) are the cube roots of unity, then \((1+\omega)\left(1+\omega^{2}\right)\left(1+\omega^{4}\right)\left(1+\omega^{8}\right)\) is equal toKCET 2007 Easy
- If \(f(x)=1+n x+\frac{n(n-1)}{2} x^2+\frac{n(n-1)(n-2)}{6}\) \(x^3+\ldots+x^n\), then \(f^n(1)\) is equal toKCET 2023 Medium
More PYQs from KCET
- The maximum value of \( \left(\frac{1}{x}\right)^{x} \) isKCET 2018 Hard
- If the function \( f(x) \) defined by
\[
f(x)=\frac{x^{100}}{100}+\frac{x^{99}}{99}+\ldots \ldots+\frac{x^{2}}{2}+x+1, \text { then } f^{\prime}(0)=
\]KCET 2014 Easy - In Young's double slit experiment with sodium vapour lamp of wavelength \(589 \mathrm{~nm}\) and the slits \(0.589 \mathrm{~mm}\) apart, the half angular width of the central maximum isKCET 2007 Medium
- A point charge is placed in a moving train. A passenger A sitting in the train and person B on the ground observe the fields due to this charge. ThenKCET 2026 Medium
- Toluene reacts with halogen in presence of iron (III) chloride giving ortho and para halo
compounds. The reaction isKCET 2017 Medium - The probability of solving a problem by three persons \(A, B\) and \(C\) independently is \(\frac{1}{2}, \frac{1}{4}\) and \(\frac{1}{3}\) respectively. Then the probability of the problem is solved by any two of them isKCET 2020 Medium