When two surface are polished, the friction coefficient between them decreases. But the friction coefficient increases and becomes very large if the surfaces are made highly smooth. Explain.

An insect crawls up a hemispherical surface very slowly (see the figure). The coefficient of friction between the insect and the surface is 1/3. If the line joining the centre of the hemispherical surface to the insect makes an angle alpha with the vertical, the maximum possible value of alpha is given by

A block weighing 40N travels down a smooth fixed curved track AB joined to a rough horizontal surface (figure). The rough surface has a friction coefficient of 0.10 with the block. If the block starts slipping on the track from a point 2.0m above the horizontal surface, the distance it will move on the rough surface is :-

A uniform cylinder of mass M lies on a fixed plane inclined at a angle theta with the horizontal. A light string is tied to the cylinder at the rightmost point, and a mass m hangs from the string as shown. Assume that the coefficient of friction between the cylinder and the incline plane is sufficiently large to prevent slipping. for the cylinder to remain static the value of m is

The coefficient of static friction between two surfaces depend on

A thin rod of length 1 m is fixed in a vertical position inside a train, which is moving horizontally with constant acceleration 4 ms^(-2) .A bead can slide on the rod and friction coefficient between them is 0.5 . If the bead is released from rest at the top of the rod , it will reach the bottom in

When force F applied on m_(1) and there is no friction between m_(1) and surface and the coefficient of friction between m_(1)and m_(2) is mu. What should be the minimum value of F so that there is on relative motion between m_(1) and m_(2)

When force F applied on m_(2) and there is no friction between m_(1) and surface and the coefficient of friction between m_(1) and m_(2) is mu. What should be the minimum value of F so that there is no relative motion between m_(1) and m_(2)

If the two blocks moves with a constant uniform speed then find coefficient of fricition between the surface of the block B and the table. The spring is massless and the pulley is fricitionless.

A box of mass m is initially at rest on a horizontal surface. A constant horizontal force of mg/2 is applied to the box directed to the right. The coefficient of friction of the surface changes with the distance pushed as mu=mu_(0)x where x is the distance fr4om the initial location . For what distance is the box pushed until it comes to rest again?

Two blocks of mass m_(1)=10kg and m_(2)=5kg connected to each other by a massless inextensible string of length 0.3m are placed along a diameter of the turntable. The coefficient of friction between the table and m_(1) is 0.5 while there is no friction between m_(2) and the table. the table is rotating with an angular velocity of 10rad//s . about a vertical axis passing through its center O . the masses are placed along the diameter of the table on either side of the center O such that the mass m_(1) is at a distance of 0.124m from O . the masses are observed to be at a rest with respect to an observed on the tuntable (g=9.8m//s^(2)) . (a) Calculate the friction on m_(1) (b) What should be the minimum angular speed of the turntable so that the masses will slip from this position? (c ) How should the masses be placed with the string remaining taut so that there is no friction on m_(1) .