Question

If a car's engine apply force equal to the kinetic friction then wouldn't the net force=0 =>
the car is at rest? Is it possible for the car to have uniform velocity on the road despite friction?

Answer 1

There are 2 kinds of friction on the road. first is 'Static friction force ' and second is 'Kinetic friction force'. Static friction force is greater than kinetic friction force. Initially car is at rest and have static friction on road . car's engine needs to apply force little more than static friction force to make the car move. then car's engine again applies more force to accelerate and gain a specific velocity. when car is in motion, kinetic friction of road acts in opposite direction of car's motion. onec car gains a specific velocity , we can put car in uniform motion . here net force =0 and applied force by engine = kinetic friction force. ''According to Newton's first Law, if an object is in motion, it will remain in motion untill a force is applied to change its motion.''' same way once car is set in motion a specifiec velocity and no net force acting on it . it will remain in motion it will not stop. as car's engine is applying enough force to overcome it kinetic friction force . so car will keep moving with same velocity. is you want to stop the car at this position then you need to apply a force in opposite direction or apply brakes . otherwise car will keep moving uniform motion.