Which of these two is incorrect?

Dear student,

There is a little difference between two concepts: velocity and speed. First of all, let's regard that you are at axis-x, to 3 meters from origin of cartesians system, so you walk to origin. Later, you walk again more 4 meters at axis-y. So, your displacement is 5 meters, according Pitagoras' theorem, but, the distance that you've covered is 7 meters. In others terms, the displacement is a vector, then, depend only two points( at this case is final point minus initial point). The distance is what you really walked. Therefore the velocity is the time variation of displacement and the speed is the time variation of distance.Hence, car is moving with constant speed is right.   Hope this helps. Team Topperlearning.com