JEE Main 2022 · 28 Jun · Shift 2 · Physics Q33

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PhysicsSingle correct+4 / -1Question 33 of 90

A block of mass 2 kg moving on a horizontal surface with speed of 4 ms $^{-1}$ enters a rough surface ranging from $x=0.5$ m to $x=1.5$ m. The retarding force in this range of rough surface is related to distance by $F=-kx$ where $k=12$ Nm $^{-1}$ . The speed of the block as it just crosses the rough surface will be :

zero

1.5 ms

^{-1}

2.0 ms

^{-1}

2.5 ms

^{-1}

Answer and worked solution

Official answer: C

Work by friction. $-\int_{0.5}^{1.5}12x\,dx=-6(2.25-0.25)=-12$ J.

Speed. $\frac12\cdot2v^2=16-12=4$ , so $v=2$ m s $^{-1}$ .

(C)

Topics:Work-energy theorem Work by constant and variable forces

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JEE Main 2022 · 28 Jun · Shift 2, Physics question 33