Question:How is relative velocity calculated?
By simply doing a vector subtraction of the two velocities.
First a sign convention must be chosen; such as RIP or right is positive.
Then one values must be subtracted from the other – it does not matter which way round, as long as you remember the signs – the sign gives the direction relative to the 1st car in you subtraction.
CAR 1= 40m/s to the right; CAR 2= 50m/s to the left.
CAR 1 = +40 m/s ; CAR 2 = -50 m/s
40 – (-50) = +90 m/s
-50 – (+40) = -90 m/s
The signs indicate the direction of the relative velocity towards the car you started from.