Consider the following three statements :
P) Any particle which moves in uniform circular motion (i.e. constant speed ) must have ZERO net force acting on it.
Q) If a non- zero net force acts on a particle, the particle’s velocity w.r.t. inertial frame will change.
R) If frictional forces are present, Newton’s second law $({\overrightarrow{F}}_{net}=m\overrightarrow{a})$  is no longer exactly true.