Question

so like im tryn figure out. still. if a car is goin 56 mph n a fly is flying as well in yo car, is that fly goin 56 mph as well?

Answer 1

for this question, the fly's speed is with respect to something. If it is with respect to the car, it is not moving, nothing has any speed if the system is the car, because the car is going but everything else inside the car is still. Think about it? when you are in a car. do you move?
with respect to the earth the fly is moving at the same speed as the car