Verified Solution • 2025–26 Session moderate

QJEEM18Ph2fd2: JEE Main 2018 Physics - Class 11 JEEM18Ph2fd2 Solution: A body of mass 2 kg slides down with an acceleration of 3 m/s 2 …

A body of mass 2 kg slides down with an acceleration of 3 m/s2 on a rough inclined plane having a slope of 30o{30^o} . The external force required to take the same body up the plane with the same acceleration will be : (g = 10 m/s2)

Multiple Choice Options

  • A 14 N
  • B 20 N
  • C 6 N
  • D 4 N

Step-by-Step Verified Solution

When mass slide down then,

Mgsin θ\theta −- μ\mu Mg cos θ\theta = Ma

⇒\Rightarrow    \,\,\, a = g(sin30o −- μ\mu cos30o)

When mass pushed upward with force F,

F −- Mgsin θ\theta −- μ\mu Mgcos θ\theta = Ma

⇒\Rightarrow    \,\,\, F = Mg(sin30o + μ\mu cos 30o) + Mg(sin30o −- μ\mu cos30o)

⇒\Rightarrow    \,\,\, F = 2Mg sin30o

= 2 ×\times 2 ×\times 10 ×\times 12{1 \over 2}

= 20 N

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