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JEE Main 2019 (12 Jan, Shift 2) · Rolling Motion

Rolling Motion question from JEE Main 2019 (12 Jan, Shift 2)

Q70JEE Main 2019 · 12 JAN · SHIFT 2Medium

Rolling Motion

A particle of mass 20 g is released with an initial velocity 5 m/s along the curve from the point A, as shown in the figure. The point A is at height h from point B. The particle slides along the frictionless surface. When the particle reaches point B, its angular momentum about O will be: (Take g = 10 m/s2)

Figure

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Answer: (a)

  1. Frictionless slide: vB2=vA2+2gh=25+2(10)(10)=225⇒vB=15v_B^2 = v_A^2 + 2gh = 25 + 2(10)(10) = 225 \Rightarrow v_B = 15 m/s.
  2. At B the velocity is horizontal and B is a+h=20a + h = 20 m below O, so this is the perpendicular distance.
  3. L=mvB(a+h)=0.02×15×20=6 kg m2/sL = m v_B (a+h) = 0.02 \times 15 \times 20 = 6\ \text{kg m}^2/\text{s}.
  4. So the answer is (a) 6 kg-m2^2/s.
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