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5.17 Areas with the y-axis and volumes of revolutionIB Maths: Analysis and Approaches HL: Subtopic test

10 questions, 27 marks

IB Maths: Analysis and Approaches HL

5.17 Areas with the y-axis and volumes of revolution

Total 27 marks

Name

Class

Date

  1. 1
    The curve CC has equation y=ln⁡xy=\ln x, for x>0x>0. The region RR is enclosed by CC, the yy-axis, the xx-axis and the line y=2y=2.
    (a)
    Which of the following gives the area of RR?
    [1 mark]
    • A∫02ey dy\displaystyle\int_{0}^{2} e^{y}\,dy
    • B∫1e2ln⁡x dx\displaystyle\int_{1}^{e^{2}} \ln x\,dx
    • C∫02ln⁡y dy\displaystyle\int_{0}^{2} \ln y\,dy
    • D∫0e2ey dy\displaystyle\int_{0}^{e^{2}} e^{y}\,dy
    (b)
    Find the area of RR.
    [1 mark]
    • Ae2e^{2}
    • Be2+1e^{2}+1
    • C2e22e^{2}
    • De2−1e^{2}-1
    (c)
    The region RR is rotated through 2π2\pi radians about the yy-axis. Find the exact volume of the solid formed.
    [2 marks]

    Total for question 1: 4 marks

  2. 2
    The region SS is enclosed by the curve y=2xy=\dfrac{2}{\sqrt{x}}, the xx-axis and the lines x=1x=1 and x=4x=4. The region SS is rotated through 2π2\pi radians about the xx-axis to form a solid of volume VV.
    (a)
    Which of the following is equal to VV?
    [1 mark]
    • Aπ∫142x dx\pi\displaystyle\int_{1}^{4}\frac{2}{\sqrt{x}}\,dx
    • B∫144x dx\displaystyle\int_{1}^{4}\frac{4}{x}\,dx
    • Cπ∫144x dx\pi\displaystyle\int_{1}^{4}\frac{4}{x}\,dx
    • Dπ∫144x2 dx\pi\displaystyle\int_{1}^{4}\frac{4}{x^{2}}\,dx
    (b)
    Find the exact value of VV.
    [1 mark]
    • A4π4\pi
    • B3π3\pi
    • C8πln⁡28\pi\ln 2
    • D2πln⁡22\pi\ln 2
    (c)
    The part of SS between x=1x=1 and x=kx=k, where 1<k<41<k<4, is rotated through 2π2\pi radians about the xx-axis. The solid formed has volume V2\dfrac{V}{2}. Find the value of kk.
    [2 marks]

    Total for question 2: 4 marks

  3. 3
    A glass bowl is modelled by rotating the part of the curve y=x24y=\dfrac{x^{2}}{4} for which 0≤y≤90\le y\le 9 through 2π2\pi radians about the yy-axis. All lengths are in centimetres. The bowl stands on a horizontal table with its axis vertical, and water is poured in until the depth of water, measured from the lowest point of the bowl, is hh cm.
    (a)
    Show that the volume of water in the bowl is 2πh22\pi h^{2} cm3^{3}.
    [3 marks]
    (b)
    The bowl is filled with water to exactly half of its total capacity. Find the depth of the water, giving your answer to three significant figures, and explain why this depth is more than half the height of the bowl.
    [4 marks]

    Total for question 3: 7 marks

  4. 4
    The curves y=xy=\sqrt{x} and y=x2y=\dfrac{x}{2} meet at the origin and at one other point. The region RR is the finite region enclosed between the two curves.
    (a)
    The region RR is rotated through 2π2\pi radians about the xx-axis. Find the exact volume of the solid formed.
    [6 marks]
    (b)
    (i) By integrating with respect to yy, find the area of RR.
    (ii) The region
    RR is rotated through 2π2\pi radians about the yy-axis. Find the exact volume of the solid formed.
    [6 marks]

    Total for question 4: 12 marks

End of questions