-- When you see the words "uniform speed", that means the car's speed is not changing.
-- Right under those words in the picture, there's a note to remind you that "uniform speed" also means "acceleration is zero".
-- The whole key to this question is to find out if you remember that acceleration and net force always go together.
.==> If there's net force, then there's acceleration.
.==> If there's acceleration, then there's net force.
.==> If there's NO net force then there's NO acceleration.
.==> If there's no acceleration, then there's no net force.
-- In this picture, there's no acceleration, so there's no net force.
-- The driving force on the car is 2000N forward.
-- But the car's speed is not changing, so the net force on the car must be zero.
-- So that 'resisting' force pulling the car backwards must be 2000N. Then the net force on the car adds up to zero.
-- If the resisting force pulling the car backwards is not zero, then the net force on the car would not be zero, and the car's speed would be changing.
