Question

you are in a car going north at 40 mi/h. (north is the positive direction.) ahead on the road, a truck is traveling south at 40 mi/h. relative to the you, what is the trucks apparent velocity? -80 mi/h 0 mi/h +40mi/h +80 mi/h -40 mi/h

Explanation:

Step1: Define velocities

Let the velocity of the car $v_{c}=40$ mi/h (positive as north - positive). The velocity of the truck relative to the road $v_{t}=- 40$ mi/h (negative as south - negative).

Step2: Calculate relative velocity

The relative velocity of the truck with respect to the car $v_{t - c}=v_{t}-v_{c}$. Substitute the values: $v_{t - c}=-40 - 40=-80$ mi/h.

Answer:

-80 mi/h