Laws of Motion & Friction · JEE Main previous year questions

2012 5 questions

1. Q362012 · 26 May 2012 · Shift 1

   A stone of mass $m$, tied to the end of a string, is whirled around in a circle on a horizontal frictionless table. The length of the string is reduced gradually keeping the angular momentum of the stone about the centre of the circle constant. Then, the tension in the string is given by $T=A{r}^n$, where $A$ is a constant, $r$ is the instantaneous radius of the circle. The value of $n$ is equal to

   1. A.$-1$
   2. B.$-2$
   3. C.$-4$
   4. D.$-3$
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   Answer: D

2. Q482012 · 26 May 2012 · Shift 1

   Currents of 10 ampere and 2 ampere are passed through two parallel thin wires $A$ and $B$ respectively in opposite directions. Wire $A$ is infinitely long and the length of the wire $B$ is $2\mathrm{m}$. The force acting on the conductor $B$, which is situated at $10\mathrm{cm}$ distance from $A$ will be

   1. A.$8\times 10^{-5}\mathrm{N}$
   2. B.$5\times 10^{-5}\mathrm{N}$
   3. C.$8\pi \times 10^{-7}\mathrm{N}$
   4. D.$4\pi \times 10^{-7}\mathrm{N}$
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   Answer: A

3. Q332012 · 12 May 2012 · Shift 1
   
   1. A.$\cot \alpha =3$
   2. B.$\sec \alpha =3$
   3. C.$\mathrm{cosec}\alpha =3$
   4. D.$\cos \alpha =3$
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   Answer: A

4. Q362012 · 12 May 2012 · Shift 1
   
   1. A.$\frac{m_2}{m_1}$
   2. B.$\frac{m_1}{m_2}$
   3. C.$\sqrt{\frac{m_2}{m_1}}$
   4. D.$\sqrt{\frac{m_1}{m_2}}$
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   Answer: A

5. Q372012 · 7 May 2012 · Shift 1

   A solid sphere having mass $m$ and radius $r$ rolls down an inclined plane. Then its kinetic energy is

   1. A.$\frac{5}{7}$ rotational and $\frac{2}{7}$ translational
   2. B.$\frac{2}{7}$ rotational and $\frac{5}{7}$ translational
   3. C.$\frac{2}{5}$ rotational and $\frac{3}{5}$ translational
   4. D.$\frac{1}{2}$ rotational and $\frac{1}{2}$ translational
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   Answer: B