Question

We want to determine experimentally the coefficients of friction between the blue block of mass ?, and the wooden plane in the figure on the right. To do so, we vary the angle of inclination of the plane and measure the value at which the block starts to move (let’s call this angle ?_#). As the block moves along the plane, we then vary the angle of inclination (either increasing or decreasing it) until the block moves with constant velocity (let’s call this angle ?_$).

a) Which of the following statements is FALSE?

1. The value of ?_# is related to the coefficient of static friction.
2. ?_# is going to be greater than ?_$.
3. The value of ?_$ is related to the coefficient of kinetic friction.
4. ?_$ is going to be greater than ?_#.

b) Draw a free body diagram for the block in the two cases:

F1.1) When the block is not moving.

F1.2) When the block moves with constant velocity.

c) Using the relevant angle determined by the experiments (?_# or ?_$) and any other required physical quantity (mass, acceleration of gravity, etc.), write an equation for:

P1.1) The coefficients of static friction.

P1.2) The coefficient of kinetic friction.

Answer 1