Question

Sphere with mass 200 g and initial velocity 2 m / s stops after 10 s under the action of friction friction force f. What is the value of this force?

Answer 1

Find the acceleration:

$$a=\frac{\Delta v}{t}=\frac{v-0}{t}=\frac vt.$$

Find the force according to Newton's second law:

$$f=ma=m\frac vt=0.04\text{ N}.$$