Laws of Motion & Friction · JEE Main previous year questions

2019 13 questions

1. Q552019 · 12 Apr 2019 · Shift 1

   A man (mass = 50 kg) and his son (mass = 20 kg) are standing on a frictionless surface facing each other. The man pushes his son so that he starts moving at a speed of $0.70{\text{ ms}}^{-1}$ with respect to the man. The speed of the man with respect to the surface is :

   1. A.$0.28{\text{ ms}}^{-1}$
   2. B.$0.47{\text{ ms}}^{-1}$
   3. C.$0.20{\text{ ms}}^{-1}$
   4. D.$0.14{\text{ ms}}^{-1}$
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   Answer: C

2. Q432019 · 12 Apr 2019 · Shift 2
   
   1. A.$3.2{\text{ ms}}^{-2}$
   2. B.$0.8{\text{ ms}}^{-2}$
   3. C.$0{\text{ ms}}^{-2}$
   4. D.$0.4{\text{ ms}}^{-2}$
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   Answer: B

3. Q422019 · 10 Apr 2019 · Shift 1
   
   1. A.$x=\left(\frac{I_1}{I_1+I_2}\right)d$ and $x=\left(\frac{I_2}{I_1-I_2}\right)d$
   2. B.$x=\left(\frac{I_2}{I_1+I_2}\right)d$ and $x=\left(\frac{I_2}{I_1-I_2}\right)d$
   3. C.$x=\left(\frac{I_1}{I_1-I_2}\right)d$ and $x=\left(\frac{I_2}{I_1+I_2}\right)d$
   4. D.$x=\pm \frac{I_{1}d}{I_1-I_2}$
   Show answer

   Answer: D

4. Q472019 · 10 Apr 2019 · Shift 2
   
   1. A.8 N
   2. B.16 N
   3. C.40 N
   4. D.12 N
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   Answer: B

5. Q482019 · 10 Apr 2019 · Shift 2

   Light is incident normally on a completely absorbing surface with an energy flux of $25\mathrm{W}\mathrm{c}{\mathrm{m}}^{-2}$. If the surface has an area of $25\mathrm{c}{\mathrm{m}}^2$, the momentum transferred to the surface in 40 min time duration will be :

   1. A.$6.3\times 10^{-4}\mathrm{Ns}$
   2. B.$5.0\times 10^{-3}\mathrm{Ns}$
   3. C.$1.4\times 10^{-6}\mathrm{Ns}$
   4. D.$3.5\times 10^{-6}\mathrm{Ns}$
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   Answer: B

6. Q522019 · 9 Apr 2019 · Shift 1

   A uniform cable of mass 'M' and length 'L' is placed on a horizontal surface such that its $(1/n{)}^{th}$ part is hanging below the edge of the surface. To lift the hanging part of the cable upto the surface, the work done should be :

   1. A.$\frac{2MgL}{n^2}$
   2. B.nMgL
   3. C.$\frac{MgL}{2n^2}$
   4. D.$\frac{MgL}{n^2}$
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   Answer: C

7. Q582019 · 9 Apr 2019 · Shift 2

   A string 2.0 m long and fixed at its ends is driven by a 240 Hz vibrator. The string vibrates in its third harmonic mode. The speed of the wave and its fundamental frequency is :-

   1. A.180m/s, 80 Hz
   2. B.180m/s, 120 Hz
   3. C.320m/s, 120 Hz
   4. D.320m/s, 80 Hz
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   Answer: D

8. Q372019 · 12 Jan 2019 · Shift 2
   
   1. A.$\frac{\sqrt{3}}{4}$
   2. B.$\frac{1}{2}$
   3. C.$\frac{\sqrt{3}}{2}$
   4. D.$\frac{2}{3}$
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   Answer: C

9. Q452019 · 12 Jan 2019 · Shift 2

   A vertical closed cylinder is separated into two parts by a frictionless piston of mass m and of negligible thickness. The piston is free to move along the length of the cylinder. The length of the cylinder above the piston is ${\ell }_1$, and that below the piston is ${\ell }_2$, such that ${\ell }_1>{\ell }_2$. Each part of the cylinder contains n moles of an ideal gas at equal temperature T. If the piston is stationary, its mass, m, will be given by : (R is universal gas constant and g is the acceleration due to gravity)

   1. A.$\frac{nRT}{g}\left[\frac{{\ell }_1-{\ell }_2}{{\ell }_1{\ell }_2}\right]$
   2. B.$\frac{RT}{g}\left[\frac{2{\ell }_1+{\ell }_2}{{\ell }_1{\ell }_2}\right]$
   3. C.$\frac{nRT}{g}\left[\frac{1}{{\ell }_2}+\frac{1}{{\ell }_1}\right]$
   4. D.$\frac{RT}{ng}\left[\frac{{\ell }_1-3{\ell }_2}{{\ell }_1{\ell }_2}\right]$
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   Answer: A

10. Q422019 · 11 Jan 2019 · Shift 2

    A particle of mass m is moving in a straight line with momentum p. Starting at time $t=0$, a force $F=kt$ acts in the same direction on the moving particle during time interval T so that its momentum changes from p to 3p. Here k is a constant. The value of T is :

    1. A.$2\sqrt{\frac{k}{p}}$
    2. B.$2\sqrt{\frac{p}{k}}$
    3. C.$\sqrt{\frac{2p}{k}}$
    4. D.$\sqrt{\frac{2k}{p}}$
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    Answer: B

11. Q342019 · 9 Jan 2019 · Shift 1
    
    1. A.$32\text{ N}$
    2. B.$18\text{ N}$
    3. C.$23\text{ N}$
    4. D.$25\text{ N}$
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    Answer: A

12. Q392019 · 9 Jan 2019 · Shift 1
    
    1. A.$\tan \theta =\frac{1}{2\sqrt{3}}$
    2. B.$\tan \theta =\frac{1}{2}$
    3. C.$\tan \theta =\frac{2}{\sqrt{3}}$
    4. D.$\tan \theta =\frac{1}{3}$
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    Answer: D

13. Q462019 · 9 Jan 2019 · Shift 1
    
    1. A.$\frac{2F}{\sqrt{mk}}$
    2. B.$\frac{F}{\pi \sqrt{mk}}$
    3. C.$\frac{\pi F}{\sqrt{mk}}$
    4. D.$\frac{F}{\sqrt{mk}}$
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    Answer: D