Polishing beyond certain limit may increase friction between the surfaces. Explain.

A rectangular box lies on a rough inclined surface at theta . The co-efficient of friction between the surface and the box is mu. Let the mass of the box is m. What is the force acting on the box down the plane, if the angle of inclination of the plane is increased to alpha>theta ?

A rectangular box lies on a rough incli ned surface. The co-efficient of friction between the surface and the box is mu. Let the mass of the box is be m. What is the force needed to be applied upwards along the plane to make the box move up the plane with acceleration alpha ?

A rectangular box lies on a rough incli ned surface. The co-efficient of friction between the surface and the box is mu. Let the mass of the box is be m. At what angle of inclination theta of the plane to the horizontal will the box just start to slide down the plane?

A rectangular box lies on a rough incli ned surface. The co-efficient of friction between the surface and the box is mu. Let the mass of the box is be m. What is the force needed to be applied upwards along the plane to make the box either remains stationary or just move up with unifrom speed?

What is the acceleration of the block and trolley system shown in the figure, if the coefficient of kinetic friction between the trolley and the surface is 0.04?/ What is the tension in the string? (Take g = 10 ms^-2 ) Neglect the mass of the string.

A mass of 4 kg rests on a horizontal plane. The plane is gradually inclined at an angle theta = 15^@ with the horizontal, the mass just begins to slide. What is the coefficient of static friction between the block and the surface?

What is the effect on interference pattern in Young's double slit experiment when separation between two slits is increased. Explain your answer in each case.