2. Why does a car speedometer only have positive values, even though you can move

in reverse?

Because it's measure the speed according to the car distance traveled and not the direction of the car movement.

Step-by-step explanation:

The newer cars have digital speedometers; the display would register as a forward speed while backing; and the odometer a positive distance as well ... In those cars the odometer could run in reverse, subtracting miles.

There actually are simple ... The newer cars have digital speedometers; the display would register as a forward speed while backing; and the odometer a positive distance as well ... In those cars the odometer could run in reverse, subtracting miles