Question

Students study the sliding of a wooden block on an inclined plane using ultrasonic radar. The inclination of the plane was adjusted so that the block slid at a constant speed. The slope angle was then 21º. The mass of the block was 275 g. Calculate the amount of friction as the block slid smoothly.

Answer 1

The force of friction is

$$f=\mu N,$$

where normal force is

$$N=mg\text{ cos}21°,$$

and the coefficient of friction is

$$\mu=\text{tan}21°.\\ f=\text{tan}21°\cdot mg\text{ cos}21°=0.966\text{ N}.$$