The differential equation representing the family of curves \(\mathrm{y}^{2}=2 \mathrm{c}(\mathrm{x}+\mathrm{v} \mathrm{c})\), where \(\mathrm{c}\) is a positive parameter, is of order and degree as follows. (A) order 2, degree 1 (B) order 1 , degree 2 (C) order 2 , degree 2 (D) order 1 , degree 3

Short Answer

Expert verified
The given equation is \(y^2 = 2c(x+vc)\), where \(c\) and \(v\) are arbitrary constants. In order to find the differential equation representing this family of curves, first eliminate these constants. After differentiating the equation with respect to \(x\), we obtain the differential equation \(0=(yy'(x+vc) - y^2)/(x+vc)^2\). The order of the differential equation is 1 (represented by \(y'\)), and the degree is also 1. So, none of the given options A, B, C, D are correct.

Step by step solution

01

Express the equation as a differential equation

The given equation is \(y^2=2c(x+vc)\). Here \(v\) and \(c\) are arbitrary constants. We need to eliminate these constants from the equation to express it as a differential equation. First replace \(c\) using \(y^2/2(x+vc)\) and differentiate the resulting equation with respect to \(x\) to eliminate \(v\).
02

Differentiate the equation

Start with the equation \(c = \frac{y^2}{2(x+vc)}\). Differentiate this equation with respect to \(x\) using chain rule: \(\frac{d}{dx}c = \frac{d}{dx}[y^2/2(x+vc)]\) Since \(c\) is a constant, it's differentiation will be zero and on the other side of the equation using quotient and chain rule: \(0=\frac{[(2yy')(2(x+vc)) - y^2(2+2vc')]}{4(x+vc)^2}\) Considering that the derivative of \(c\) with respect to \(x\) is zero (\(c' = 0\)), the equation simplifies to: \(0=\frac{(2yy')(2x+2vc) - 2y^2}{4(x+vc)^2}\) Then after simplifying it we get: \(0=(yy'[x+vc] - y^2)/(x+vc)^2\)
03

Identify the order and degree

The revised equation is a differential equation. We can see the order and degree of this differential equation. Order of a differential equation is basically the order of the highest order derivative present in the equation. Degree is the power of the highest order derivative in the equation only if the differential coefficients in the equation are free from radicals and fractions. Here in \(0=(yy'[x+vc] - y^2)/(x+vc)^2\), the highest order of derivative is 1 (which is \(y'\)). The power of this highest order derivative is also 1 since it is not under any radical or fractional power. Hence, the order of the differential equation is 1 and the degree is 1. So, none of the given options A, B, C, D are correct.

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Most popular questions from this chapter

The differential equation of all parabolas having axis parallel to y-axis: (A) \(\left(\mathrm{d}^{3} \mathrm{x} / \mathrm{dy}^{3}\right)^{2}=0\) (B) \(\left(\mathrm{d}^{3} \mathrm{y} / \mathrm{dx}^{3}\right)=0\) (C) \(\left(\mathrm{d}^{3} \mathrm{y} / \mathrm{dx}^{3}\right)+\left(\mathrm{d}^{2} \mathrm{y} / \mathrm{d} \mathrm{x}^{2}\right)=0\) (D) \(\left(\mathrm{d}^{2} \mathrm{y} / \mathrm{dx}^{2}\right)=0\)

The solution of \((\mathrm{dx} / \mathrm{dy})=\left[1 /\left(2 \mathrm{x}-\mathrm{y}^{2}\right)\right]\) is: (A) \(x=c \cdot e^{2 y}+(1 / 2) y^{2}+(1 / 2) y+(1 / 4)\) (B) \(x=c \cdot e^{-y}+(1 / 4) y^{2}+(1 / 4) y+(1 / 2)\) (C) \(\mathrm{y}=\mathrm{c} \cdot \mathrm{e}^{-2 \mathrm{x}}+(1 / 4) \mathrm{x}^{2}+(1 / 2) \mathrm{x}+(1 / 4)\) (D) \(x=c \cdot e^{y}+(1 / 4) y^{2}+y+(1 / 2)\)

\((\mathrm{dy} / \mathrm{dx})=\mathrm{e}^{\mathrm{x}+\mathrm{y}}+\mathrm{x}^{2} \mathrm{e}^{\mathrm{y}}\) has the particular solution for \(\mathrm{x}=\mathrm{y}\) \(=0:\) (A) \(\mathrm{e}^{\mathrm{x}}-\mathrm{e}^{-\mathrm{y}}+\left(\mathrm{x}^{3} / 3\right)=2\) (B) \(\mathrm{e}^{\mathrm{x}}+\mathrm{e}^{-\mathrm{y}}+\left(\mathrm{x}^{3} / 3\right)=2\) (C) \(\mathrm{e}^{\mathrm{x}-\mathrm{y}}+\left(\mathrm{x}^{3} / 3\right)=2\) (D) \(e^{y-x}-\left(x^{3} / 3\right)=2\)

If the general solution of \((\mathrm{dy} / \mathrm{dx})=(\mathrm{y} / \mathrm{x})+\mathrm{f}(\mathrm{x} / \mathrm{y})\) is \(\mathrm{y}\) \(=[\mathrm{x} / \log |\mathrm{cx}|]\), then \(\mathrm{f}(\mathrm{x} / \mathrm{y})\) is given by: (A) \(\left(\mathrm{x}^{2} / \mathrm{y}^{2}\right)\) (B) \(\left(\mathrm{y}^{2} / \mathrm{x}^{2}\right)\) (C) \(\left[\left(-\mathrm{x}^{2}\right) / \mathrm{y}^{2}\right]\) (D) \(\left[\left(-\mathrm{y}^{2}\right) / \mathrm{x}^{2}\right]\)

\(\underline{\text { Assertion - Reason Type Questions: }}\) Each question has four choices (a), (b), (c) and (d) out of which only one is correct. Write (a), (b), (c) and (d) according to the following rules. (a) Statement- 1 is True, Statement-2 is True, Statement- 2 is a correct explanation for Statement-1. (b) Statement-1 is True, Statement- 2 is True, Statement-2 is not a correct explanation for Statement-1. (c) Statement- 1 is True, Statement- 2 is False. (d) Statement- 1 is False, Statement- 2 is True. Statement \(-2:\) The differential equation \(\mathrm{y}^{\prime}=(\mathrm{y} / 2 \mathrm{x})\) is variable separable. Statement-1: Curve satisfying the differential equation \((\mathrm{dy} / \mathrm{dx})=(\mathrm{y} / 2 \mathrm{x})\) passing through \((2,1)\) is a parabola with Focus \([(1 / 4), \underline{0}]\). Statement- 2 : The differential equation \((\mathrm{dy} / \mathrm{dx})=(\mathrm{y} / 2 \mathrm{x})\) is variable separable.

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