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Work Power and Energy question

2024 · 9 Apr · Shift 2 · Q85
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Work Power and Energy question

2024 · 9 Apr · Shift 2 · Q85

JEE MainPhysicsWork Power and EnergyNumerical+4 / −1
A force (3x2+2x−5)N(3 x^2+2 x-5) \mathrm{N}(3x2+2x−5)N displaces a body from x=2 mx=2 \mathrm{~m}x=2 m to x=4 mx=4 \mathrm{~m}x=4 m. Work done by this force is ‾\underline{\hspace{2cm}}​ J.
Numerical answer
View written solutionFree

Correct answer: 58

  1. Given force as a function of position

    F(x)=3x2+2x−5F(x) = 3x^2 + 2x - 5F(x)=3x2+2x−5

    The body moves from:

    x=2 m to x=4 mx=2\text{ m to }x=4\text{ m}x=2 m to x=4 m

  2. Formula for work done by a variable force

    Work done is the integral of force with respect to displacement:

    W=∫24F(x) dx=∫24(3x2+2x−5) dxW = \int_{2}^{4} F(x)\,dx = \int_{2}^{4} (3x^2+2x-5)\,dxW=∫24​F(x)dx=∫24​(3x2+2x−5)dx

  3. Integrate the function

    ∫(3x2+2x−5) dx=x3+x2−5x\int (3x^2+2x-5)\,dx = x^3 + x^2 - 5x∫(3x2+2x−5)dx=x3+x2−5x

  4. Apply the limits

    W=[x3+x2−5x]24W = \left[x^3 + x^2 - 5x\right]_{2}^{4}W=[x3+x2−5x]24​

    At x=4x=4x=4:

    43+42−5(4)=64+16−20=604^3 + 4^2 - 5(4) = 64 + 16 - 20 = 6043+42−5(4)=64+16−20=60

    At x=2x=2x=2:

    23+22−5(2)=8+4−10=22^3 + 2^2 - 5(2) = 8 + 4 - 10 = 223+22−5(2)=8+4−10=2

    Therefore,

    W=60−2=58 JW = 60 - 2 = 58\text{ J}W=60−2=58 J

  5. Final answer

    58\boxed{58}58​

  6. Comparison with stored correct answer

    Stored correct answer = 585858

    My derived answer also = 585858, so they agree.

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