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Concepts Of Physics MCQ Edition [Volume 1]
Exam
Concepts Of Physics MCQ Edition [Volume 1]
Subject
Physics
Chapter
Friction

Concepts Of Physics MCQ Edition [Volume 1] · Physics · Friction

A body of mass 2 kg is situated on a rough inclined plane of...

A body of mass 2 kg2 \text{ kg} is situated on a rough inclined plane of inclination 30^{}^{{}^{\circ}}. Determine the magnitude of the force parallel to the incline needed to make the block move up the incline. The coefficient of static friction is 0.20.2.

Options

  1. A10 N10 \text{ N}
  2. B16 N16 \text{ N}
  3. C13 N13 \text{ N}
  4. D6.5 N6.5 \text{ N}

Correct answer

C. 13 N13 \text{ N}

Step-by-step solution

The force required to move the block up the rough inclined plane must overcome both the component of gravity along the incline and the maximum static friction.

The component of gravity parallel to the incline is:

Fg=mgsin⁡θF_g = mg \sin \theta

The normal force is:

N=mgcos⁡θN = mg \cos \theta

The maximum static friction force is:

fs=μsN=μsmgcos⁡θf_s = \mu_s N = \mu_s mg \cos \theta

The total force FF required to move the block up the incline is:

F=Fg+fs=mgsin⁡θ+μsmgcos⁡θF = F_g + f_s = mg \sin \theta + \mu_s mg \cos \theta

Substituting m=2 kgm = 2 \text{ kg}, \theta = 30^{}^{{}^{\circ}}, μs=0.2\mu_s = 0.2, and g=9.8 m/s2g = 9.8 \text{ m/s}^2:

F = 2 \times 9.8 \times \sin 30^{}^{{}^{\circ}} + 0.2 \times 2 \times 9.8 \times \cos 30^{}^{{}^{\circ}}

F=19.6×0.5+3.92×32F = 19.6 \times 0.5 + 3.92 \times \dfrac{\sqrt{3}}{2}

F=9.8+1.96×1.732F = 9.8 + 1.96 \times 1.732

F=9.8+3.39=13.19 NF = 9.8 + 3.39 = 13.19 \text{ N}

The closest given option is 13 N13 \text{ N}.
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