JEE Main 2016 · 9 Apr · Shift 1 · Physics Q5

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PhysicsSingle correct+4 / -1Question 5 of 90

A cubical block of side 30 cm is moving with velocity 2 ms $^{-1}$ on a smooth horizontal surface. The surface has a bump at a point O as shown in figure. The angular velocity (in rad/s) of the block immediately after it hits the bump, is :

A cubical block of side a = 30 cm sliding to the right along a horizontal surface towards a bump at O.

5.0

6.7

9.4

13.3

Answer and worked solution

Official answer: A

Angular momentum about the bump O is conserved: $mv\frac a2=I_O\omega$ , with $I_O=\frac{ma^2}6+\frac{ma^2}2=\frac23ma^2$ . So
$\omega=\frac{3v}{4a}=\frac{3\times2}{4\times0.3}=5\text{ rad/s}.$

Topics:Angular momentum and its conservation Moment of inertia

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JEE Main 2016 · 9 Apr · Shift 1, Physics question 5