two sufaces are in contact but are at rest relative toeach other. neverthless each exerts a force of frictiono

Question

this is the question of physics of BSc level

Answer 1

True statement. Where's the question?

Answer 2

As said above "there is no question," but reading into your statement, I believe there is an implied question, which is "what are the forces on the two surfaces?" That is straightforward.

Because the two surfaces are not accelerating (a = 0), there is no net force (f) on the two objects (the system) having the respective surfaces. That is, f = Ma = 0 = (B - R); where B is the force on the one object (e.g., a block of wood) and R is the force on the other (e.g., a ramp).

Thus, B = R; where the force on the block is B = kN; where N is its normal weight N = W cos(theta) and k is the coefficient of friction. Theta is the angle of incline for the ramp and W = mg = the weight of the block of mass m and g is acceleration due to gravity (e.g., 9.81 m/sec^2 on Earth's surface).

Bottom line, the forces on the one surface cancel out the forces on the other surface and result in no acceleration of the one surface over the other. Since v = 0, at rest relative to each other, k is called the coefficient of static friction.

But, and this is a BIG BUT, B = R is also feasible if the one surface were sliding at a constant relative velocity v = constant. In which case k would be the coefficient of sliding friction. The point is this...the net forces might be zero f = 0 = ma; so that a = 0 even if the two surfaces were moving relative to each other, but they were not accelerating.

Answer 3

There is no question