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Work, Energy and Power · NEET Preparation Physics

A block of mass 2 kg is pulled up a smooth inclined plane of inclination 30^circ with a constant velocity of 2text{ m/s} for a displacement of 4text{…

Practice question from Work, Energy and Power (NEET Preparation Physics), with the correct answer and a step-by-step solution.

easy · MCQ · Q-9E029B

A block of mass 2 kg is pulled up a smooth inclined plane of inclination 30∘30^\circ with a constant velocity of 2 m/s2\text{ m/s} for a displacement of 4 m4\text{ m} along the plane. The work done by the gravitational force on the block is (take g=10 m/s2g = 10\text{ m/s}^2):

  1. A.-40 JCorrect answer
  2. B.+40 J
  3. C.-80 J
  4. D.0 J

Solution

The work done by gravity is given by Wg=−mghW_g = -mg h, where h=dsin⁡θh = d \sin\theta. Here, m=2 kgm = 2\text{ kg}, g=10 m/s2g = 10\text{ m/s}^2, d=4 md = 4\text{ m}, and θ=30∘\theta = 30^\circ. Thus, h=4sin⁡(30∘)=2 mh = 4 \sin(30^\circ) = 2\text{ m}. Wg=−(2)(10)(2)=−40 JW_g = -(2)(10)(2) = -40\text{ J}.

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