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MHT CET 2023 (9 May, Shift 1) · Conservation of Energy

Conservation of Energy question from MHT CET 2023 (9 May, Shift 1)

Q18MHT CET 2023 · 9 MAY · SHIFT 1Medium

Conservation of Energy

A stone is projected vertically upwards with speed 'vv'. Another stone of same mass is projected at an angle of 60∘60^\circ with the vertical with the same speed 'vv'. The ratio of their potential energies at the highest points of their journey is [sin⁡30∘=cos⁡60∘=0.5,cos⁡30∘=sin⁡60∘=32]\left[\sin 30^\circ = \cos 60^\circ = 0.5, \cos 30^\circ = \sin 60^\circ = \frac{\sqrt{3}}{2}\right]

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Answer: (a)

  1. PE at the top =mgH= mgH with H=uy22gH = \frac{u_y^2}{2g}, so U∝uy2U \propto u_y^2.
  2. Vertical stone: uy=vu_y = v. Other stone (at 60∘60^\circ with vertical): uy=vcos⁡60∘=v2u_y = v\cos 60^\circ = \frac{v}{2}.
  3. U1U2=v2v2/4=4\frac{U_1}{U_2} = \frac{v^2}{v^2/4} = 4
  4. So the answer is (a) 4:14 : 1.
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