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Laws of Motion — Physics STD 11 — Question

Tamilnadu BoardEnglish MediumSTD 11PhysicsLaws of Motion3 Marks
Question
A rectangular box lies on a rough inclined surface. The coefficient of friction between the surface and the box is (µ). Let the mass of the box be m.
  1. At what angle of inclination θ of the plane to the horizontal will the box just start to slide down the plane ?
  2. What is the force acting on the box down the plane, if the angle of inclination of the plane is increased to a > θ.
  3. What is the force needed to be applied upwards along the plane to make the box either remain stationary or just move up with uniform speed ?
  4. What is the force needed to be applied upwards along the plane to pk kg f make the box move up the plane with acceleration a ?
✓

Answer

1. When the box just starts sliding
$
\mu=\tan \theta
$
or $0=\tan ^{-1} \mu$
2. Force acting on the box down the plane $=m g(\sin a-\mu \cos a)$
3. Force needed $m g(\sin a+\mu \cos a)$
4. Force needed $=m g(\sin a+\mu \cos a)+m a$.
Image

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