The handle of a floor mop makes an angle `theta ` with the vertical. If `mu_(k) and mu_(s)` be the coefficients of kinetic and static friction between floor and mop, show that if `theta` is smaller than certain value `theta_(0)`, the mop cannot be made to slide over across the floor, no matter how great a force is directed along the handle towards the centre. What is the angle `theta_(0)` ?

A block placed on a horizontal surface is being pushed by a force F making an angle theta with the vertical as shown in Fig. 7.39 . The coefficient of friction between block and surface is mu . (a) Find the force required to slide the block with uniform velocity on the floor . (b) Show that if theta is smaller than a certain angle theta_(0) , the block cannot be made to slide across the floor , no matter how great the force be .

If mu = coefficient of friction and theta is the angle of friction, then

If mu_(s ) is coefficient of static friction and mu_(k) is coefficent of kinetic friction then

A man drags an m kg crate across a floor by pulling on a rope inclined at angle theta above the horizontal. If the coefficient of static friction between the floor and crate is then the tension required in the rope to start the crate moving is :

Find theta at which slipping will start. mu_(s) is coefficient of static friction. (Angle of repose)

If mu_k is the coefficient of kinetic friction, mu_r the coefficient of rolling friction and mu_s the coefficient of static friction, then

A box, heavier than you is placed on a rough floor. The coefficient of static friction between the box and the floor is the same as that between your shoes and the floor. Can you displace the box across.the floor.

In Q.48 , the block can be made to slide on the floor only if theta is more than a minimum value . Otherwise , the block cannot be made to slide by any value of F however large . Minimum value of theta for less than which sliding cannot happen , is :