Question Paper: Engineering Mathematics-2 : Question Paper Jun 2015 - First Year Engineering (Semester 2) | Pune University (PU)
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## Engineering Mathematics-2 - Jun 2015

### First Year Engg (Semester 2)

TOTAL MARKS: 50
TOTAL TIME: 2 HOURS
(1) Solve Q.1 or Q.2, Q.3 or Q.4, Q.5 or Q.6, Q.7 or Q.8
(2) Assume suitable data, if necessary.

### Answer any one question from Q1 and Q2

1 (a) Solve the following differential equations: $$i) \ \ \dfrac {dy}{dx} = \cos x \cos y + \sin x \sin y \\ ii) \ (x^2 + y^2 +1) dx - 2xy \ dy =0$$(8 marks) 1 (b) In a circuit containing inductance L, resistance R and voltage E, the current I is given by: $$E=RI + L \dfrac {dI}{dt}$$ Given:
L=640H, R=250 Ω, E=500 Volts. I being zero when t=0. Find the time that elapses before it reaches 80% of its maximum value.
(4 marks)
2 (a) Solve$$x \dfrac {dy}{dx}+y=y^2 \log x$$(4 marks) 2 (b) Solve the following: i) A body at temperature 100°C is placed in a room whose temperature is 20°C and cools to 60°C in 5 minutes. Find its temperature after a further interval of 3 minutes.
(ii) A steam pipe 20 cm in diameter is protected with a covering 6 cm thick for which the coefficient of thermal conductivity is k = 0.003 cal/cm deg. sec in steady state. Find the heat lost per hour through a meter length of the pipe, if the surface of pipe is at 200°C and outer surface of the covering is at 30°C.
(8 marks)

### Answer any one question from Q3 and Q4

3 (a) Find a half range cosine series of f(x) =πx-x2 in the interval 0<x&lt;&pi;&lt; a="">

</x&lt;&pi;&lt;&gt;<>(5 marks)
3 (b) Evaluate: $$\int^\infty_0 \dfrac {x^3}{3^x} dx$$(3 marks) 3 (c) Trace the following curve (any one):
i) y2=x5 (2a-x)
ii) r=a sin 2θ
(4 marks)
4 (a) $$If \ I_n = \int^{\pi /2}_{\pi /4} \cot^n \theta d \theta \\ prove \ that \ I_n=\dfrac{1}{n-1}- I_{n-2}. Hence \ evaluate \ I_3.$$(4 marks) 4 (b) Using differentiation under Integral sign prove that: $$\int^\infty _{0} \dfrac {e^{-x}-e^{-ax}}{x \sec x}dx = \dfrac {1}{2} \log \left ( \dfrac {a^2+1}{2} \right )$$ for a>0.(4 marks) 4 (c) Find the length of the curve
x=a(θ- sin θ), y=a (1-cos θ) between θ=0 to θ=2 π.
(4 marks)

### Answer any one question from Q5 and Q6

5 (a) Show that the plane 4x-3y+6z-35=0 is tangential to the sphere x2+y2+z2-z-2z-14=0 and find the point of contact.(5 marks) 5 (b) Find the equation of the right circular cone whose vertex is given by (-1, -1, 2) and axis is the line $$\dfrac {x-1}{2} = \dfrac {y+1}{1} = \dfrac {z-2}{-2}$$ and semi-vertical angle is 45°.(4 marks) 5 (c) Find the equation of right circular cylinder of radius 2 and axis is given by:
$$\dfrac {x-1}{2} = \dfrac {y-2}{-3}= \dfrac {z-3}{6}$$
(4 marks)
6 (a) Find the equation at the sphere through the circle x2+y2+z2=1, 2x+3y+4z=5 and which intersects the sphere x2+y2+z2+3 (x-y+z)-56=0 orthogonally.(5 marks) 6 (b) Find the equation of right circular cone with vertex at origin making equal angles with the co-ordinate axes and having generator with direction cosines proportional to 1, ?2, 2.(4 marks) 6 (c) Obtain the equation of the right circular cylinder of radius 5 where axis is: $$\dfrac {x-2}{3}= \dfrac {y-3}{1}= \dfrac {z+1}{1}$$(4 marks)

### Attempt any two of the following:

7 (a) Change the order of integration in the double integral: $$\int^5_0 \int^{2+x}_{2-x} f(x,y) dy \ dx$$(6 marks)

### Answer any one question from Q7 and Q8

7 (b) Evaluate: $$\int^2_0 \int^x_0 \int^{2x+2y}_0 e^{x+y+z}dx \ dy \ dz$$(7 marks) 7 (c) Find the centroid of the loop of the curve: r2=a2 cos 2 θ.(6 marks)

### Attempt any two of the following:

8 (a) Evaluate: $$\int^a_0 \int^{\sqrt{a^2-x^2}}_0 e^{-x^2 - y^2}dx dy.$$(6 marks) 8 (b) Evaluate: $$\iiint \sqrt{1- \dfrac {x^2}{a^2} - \dfrac {y^2}{b^2} - \dfrac {z^2}{c^2}}dx \ dy \ dz$$ through the volume of ellipsoid $$\dfrac {x^2}{a^2} + \dfrac {y^2}{b^2}+ \dfrac {z^2}{c^2}=1$$(6 marks) 8 (c) Prove that the moment of inertia of the area included between the curves y2=a ax and x2=4ay about x-axis is 144/35 Ma2 where M is the mass of the area included between the curves.(7 marks)