Section-C: Comprehension Type
Frictional forces are forces in nature that are not always unncessary. For example, the force of friction between the tires of a car and the road is the reason why the tires can grip without slipping. The frictional force between two surfaces depends on the nature of the materials with which the surfaces are made. Such dependence is exhibited through the use of a dimensionless quantity known as the coefficient of friction. If the two surfaces in contact are not moving with respect to each other, the maximum force of friction acting between the surfaces is proportional to the normal force between the two surfaces, with the constant of proportionality being the coefficient of friction µs. In the given figure, the coefficients of friction for contact between the inclined surface and the four boxes A,B,C and D are equal to 0.2 , 0.5, 2 and 5 respectively. All the boxes have same mass.
The box A is glued to the top of box B and others are removed. What is the effect on the maximum angle that the incline can have before the two boxes slide down by themselves? Compare it to the case when A alone is kept on the incline.