In which situation is the speed of the car constant while its velocity is changing?

Question 1 options:

A The car begins from rest and accelerates to 20 m/s

The car begins traveling at 30 m/s and slows to 15 m/s.

The car travels down a straight track at 30 m/s.

The car travels around a circular track at 30 m/s.

The car travels around a circular track at 30 m/s.