Solved question paper for MATHS-1 May-2018 (B-TECH 1st-2nd)

Solved Question Paper

Engineering mathematics-1 May-2018

PTU • B-TECH • Mechanical Engineering • 1st-2nd • May-2018

engineering mathematics-1 previous year question papers on BRpaper are organized for students of Punjab Technical University’s Bachelor of Technology program, 1st-2nd semester. This section makes it easier to browse subject-wise old question papers for engineering mathematics-1, so students can review how questions are typically framed in past exams and get a sense of the exam pattern. Many students search for engineering mathematics-1 syllabus while preparing for exams, and this page is built to support exactly that kind of subject-wise browsing and revision. BRpaper is not the official website of Punjab Technical University or any institution, and it does not publish official notices or academic updates.

Solved Questions

Solved
  1. Section A

    1. a) Find asymptotes, parallel to axes, of the curve: y = 

    Very Short Answer May-2018 • PTU B-TECH

    (a) yx- y = x+ 1

    || to x axis

              X2=0

              X = 0                    No asymptote || to x axis

    || to y axis

            X2-1 = 0

                X= 1

                X = 1

  2. Write a formula to find the volume of the solid generated by the revolution, about
    x-axis, of the area bounded by the curve y = f(x), the x-axis and the ordinates
    x = a and x = b.

    Very Short Answer May-2018 • PTU B-TECH

    (b) Volume will be given by integrating the terms

                 =  

                 =  

  3. Find the value of  , where x = rcosθ & y = rsinθ .

    Very Short Answer May-2018 • PTU B-TECH

  4. If an error of 1% is made in measuring the major and minor axes of an ellipse, what is the
    percentage error in its area?

    Very Short Answer May-2018 • PTU B-TECH

    (d) let x and y be semi major and semi minor axes of an ellipse.

                                            Area of ellipse = A=

                                            Log A = Logπ + Log x +Log y

     1+1=2

                                             Error in area = 2 %

  5. Is the function  ? If yes, what is its degree?

    Very Short Answer May-2018 • PTU B-TECH

    Yes, Degree = 2

  6. What is the value of   over the positive quadrant of the circle x2 + y2 = 1?

    Very Short Answer May-2018 • PTU B-TECH

    =

  7. Give geometrical interpretation of  

    Very Short Answer May-2018 • PTU B-TECH

     

      =  

      =    

      =    

      =   2

  8. Show that for the vector field  (x2 - y2 + x)  — (2xy + y)   = 0.

    Very Short Answer May-2018 • PTU B-TECH

        =

           =

            = -2y + 2y

               [  ]

  9. Show that the vector field  = (-x2 + yz)   + (4y — z2x) + (2xz — 4z)  is solenoidal.

    Very Short Answer May-2018 • PTU B-TECH

    For solenoidal function

    div 

    div f =   

    = -2x + 4 + 2x -4

    = 0

    So it is solenoidal

  10. State Green’s theorem in plane.

    Very Short Answer May-2018 • PTU B-TECH

    Green’s theorem in plane:-

    Let R bed closed region of x-y plane bounded by a simple closed cense c and let M and N be continuous function of x and y having continuous partial derivative  and  in R then:

  11. Section B

    2. Trace the following curves by giving their salient feature:
    a) y(a — x) = x(a + x).
    b) r = a (1 — cosθ)

    Short Answer May-2018 • PTU B-TECH

    (a) Symmetry:  Symmetrical about x-axis

    Origin: passes through origin and tangent at origin

           y= x and y =-x   therefore origin is a node.

          Asymptotes x = a

     Points:  it crones the Ares at (0,0) and  (-a,0 )

          When x >a  or  <-a    y is imaginary

    Shape of curve is strophoid      

    (b) Given figure is a cardioid and symmetrical about q = 0 i.e. initial line.

    q  varies from (0-π/2 ) or (0-180).

     

  12. a) Find the whole length of the curve  x2/3  + y2/3 = a2/3 .

    b) Use definite integral to find the area of ellipse  

    Short Answer May-2018 • PTU B-TECH

    (a) Given curve is asteroid. Which is symmetrical about x-axis and y-axis therefore entries length of curve is four times the length of one part.

       Diff given curve w.r.t x

    2/3x-1/3+ 2/3y-1/3dy/dx =0

              2/3y-1/3dy/dx = -2/3x-1/3

    dy/dx=-(y/x)1/3

    total length = 4    = 4 

     = 4 

    = 6a

    (b)   

          Therefore area of ellipse = 4x area of ellipse in I quadrant.

            =

            =

    =

     

    Therefore required area = area of region PQRS

     = 4 x area of region OFPB in the first quadrant


      =

      = 

      = 

  13. a) lf u = log (x3 +y3 +z3 —3xyz), show that  =   -9(x+y+z)-2

    b) State Euler’s theorem for homogeneous functions and apply it to show that
      ,   where sin u  =

    Short Answer May-2018 • PTU B-TECH

    (a) 

           =

     

                                            = 

                                            =

                                            =

    (b)  Euler’s theorem  

                  If H= f (x, y, z)is ahomogeneous function of x, y and z of degree n, then

    U= sin-1(x2+y2/x+y)

           Sin u = x2+y2/x+y

          F =   x2+y2/x+y

    Which is homogeneous of degree 1.

     By Euler’s theorem  

              =

  14. 5. a) The temperature T at any point (x, y, z) in space is T = 400xyz2 . Find the highest
    temperature on the surface of the unit sphere x2 + y2 + z2= 1.

    b) If f(x,y) = tan-1 xy, compute f(0.9, –1.2) approximately.

    Short Answer May-2018 • PTU B-TECH

    (a) Temperature at any point on sphere is given by

                  T= 400 xy (1-x2-y2)

      = 400y -400y3-1200x2y

    400x – 1200xy2-400x3

     For critical points

    400y-400y3-1200x2y

      400x(1-3y2-x2)=0

    critical points after solution above equation are

    (0,0),(±1,0),(0, ±1),( ±1/2, ±1/2) out of which first three given the value of T to be zero. For other four point (±1/2, ±1/2). Now A = =  2400 xy, B =   = 400-1200y2-1200x2, C= = -2400xy

    At (1/2,1/2,) A= -600 <  0, B= -200, C = -600 so that AC-B2= 320000> 0

     T is maximum at(1/2,1/2)

                                          Whose maximum value will be given by

                                   = 400 ¼(1 -1/4 - 1/4) = 100 x ½ =50

     

    (b)  f(x,y) = tan-1xy

       Let x=0.9  , y=-1

    X+δx= 0.9      1+δx=0.9                =δx=-1            =   

         -y+ δy=-1.2       δy=-1.2+1            = δy = -0.2

    df=                        = y/1+x2y2  dx + x/1+x2y2dy = ydx+xdy/1+x2y2

        When x =1

                   Y = -1

    df =

                           =   =   = 

  15. Section C

    6. a) Evaluate the following integral by changing the order of integration:

    b) Evaluate the triple integral   

    Long Answer May-2018 • PTU B-TECH

    (a) Given region of integration

             0

    it is a circle of radius 1

    we will introduce a vertical strip which will vary from

    order to change the order into integration

    = 2

    (b  =

                     = 

                     = 

                     = 

                    = 

                    = 

                    = 

  16. a) Find a unit vector normal to the surface x2+y2+z2= 9 at the point (2, -1, 2) .

    b) If u = x2+y2+z2 & Show that Ñ.  = 5u

    Long Answer May-2018 • PTU B-TECH

    (a) f(x,y,z) = x2+y2+z2 = 9

    =2x

     = 2y

     = 2z

                      Vector =

         A point (2,-1,2)

    =

     Unit vector normal to it =      

    (b) u= x2+y2+z2

    (by identity)

    )

             =

                    [ ]

  17. a) If   evaluate,  where C is the curve in the xy-plane y = 2x2
    from (0,0) to (1,2).

    (b) Compute  , where   and S is the triangular surface with vertices (2, 0,0), (0, 2, 0) and (0, 0, 4).

    Long Answer May-2018 • PTU B-TECH

    (a)    where

                  y =

       and  

     

    (b)   

    Equation of given plane x/2+y/z+z/4=1

    Let R be orthogonal projection of x+y +z/2=1in XoY plane i.e. z=0 given by x+y=1

    Therefore R=0{(x.y):0 y 1-x;0 x 1}

    =x +yx

    =(x )

    ds =

                                     [Put x=2,y=2,z=neglected ]

  18. State Gauss Divergence theorem and verify it for    taken over
    the cube bounded by x = 0, x = 1, y = 0, y = 1, z = 0, z = 1.

    Long Answer May-2018 • PTU B-TECH

    Surface contains six faces

     (i) OABC faces Z = 0,

     .

    (ii) On face DEFG Z = 1,

    (iii) On face OAFG y = 0,

    (iv) On face DEBC y = 0,

    (v) On face ABEF x = 1,

    (vi) On face OCDG x = 0,

    Gauss Divergence theorem

    If   be a vector point function having continuous first partial derivative in reason v bounded by surface (s).

    Then

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04 What kind of topics does engineering mathematics-1 usually cover?

The question papers here relate to the official engineering mathematics-1 syllabus set by the university for this course and semester.

05 Does this page include a engineering mathematics-1 syllabus or solved answers?

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