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Acceleration Of Block Against Friction - Practice Questions & MCQ

Edited By admin | Updated on Sep 18, 2023 18:34 AM | #JEE Main

Quick Facts

  • Acceleration of block against friction is considered one of the most asked concept.

  • 17 Questions around this concept.

Solve by difficulty

Consider a car moving on a straight road with a speed of 100 m/s the distance (in meters) at which the car can be stopped is \left [ \mu _{k} = 0.5\right ]

A bullet loses \left ( \frac{1}{n} \right )^{th}of its velocity passing through one plank. The number of such planks that are required to stop the bullet can be :

A body of mass 10 \mathrm{~kg} is moving with an initial speed of 20 \mathrm{~m} / \mathrm{s}. The body stops after 5 \mathrm{~s} due to friction between the body and the floor. The value of the coefficient of friction is: (Take acceleration due to gravity .g=10 \mathrm{~ms}^{-2})

Concepts Covered - 1

Acceleration of block against friction

 

  • Case 1:- Acceleration of a block on a horizontal surface

 

  • When the body is moving under the application of force P, then kinetic friction opposes its motion.

              Let a is the net acceleration of the body.

      

           From the figure,

               \\ \mathrm{P-f_{k}=ma}\\ \\ {a=\frac{P-f_{k}}{m}}

  • Case 2:- Acceleration of a block sliding down over a rough inclined plane

 

  • When the angle of the inclined plane is more than the angle of repose, the body placed on the inclined plane slides down with an acceleration a.

            

               From the figure,

\mathrm{ma=mg\ sin \theta - f_{k}}

\mathrm{ma=mg\ sin \theta - \mu R}

\mathrm{ma=mg\ sin \theta - \mu mg cos\theta}

\mathrm{a=g[sin \theta-\mu cos \theta]}

For \mu=0   \mathrm{\therefore\ \;a=g\;sin\theta}

  • Case 3:- Retardation of a block sliding up over a rough inclined plane

 

  • When the angle of the inclined plane is less than the angle of repose, then for the upward motion (with some initial velocity)

                             

                    \mathrm{ma=mg\ sin\theta+f_{k}}

\mathrm{ma=mg\ sin\theta+\mu mg\ cos\theta}

\mathrm{ma=g[sin\theta+\mu cos\theta]}

\mathrm{a=g[sin\theta+\mu cos\theta]}

For \mathrm{\mu=0}

\mathrm{a=g\ sin\theta}

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Acceleration of block against friction

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