Q9 of 57 Page 96

A block A kept on an inclined surface just begins to slide if the inclination is 30°. The block is replaced by another block B and it is found that it just begins to slide if the inclination is 40o.

All three situations are possible. It is because when the body starts sliding, the coefficient of static friction μ becomes equal to tan θ, irrespective of their masses.

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A boy of mass M is applying a horizontal force to slide a box of mass M’ on a rough horizontal surface. The coefficient of friction between the shoes of the boy and the floor is μ and that between the box and the floor is μ’. In which of the following cases it is certainly not possible to slide the box?

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