Q. A block is placed on a horizontal surface whose coefficient of friction is . A horizontal force first acts on it in the eastward direction. Later, in addition to a second horizontal force acts on it in the northward direction : (Take )

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The block will not move when only acts, but will move when both and act

If the block moves, the acceleration will be

When the block moves, its direction of motion will be east of north

When both and act, the direction of the force of friction acting on the block will be west of south

Solution:

As , friction force
and block do not move
When both and acts, resultant applied force,

, thus block moves when both and acts

Direction of ,

(east of north)

Thus, direction of force of friction will be opposite to , i.e. west of south.

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