What would happen if you shot a ball with a speed of 60 mph from the back a car traveling at 60 mph? Would the ball remain stationary? Yup—that’s exactly what the MythBusters did. That animation is so awesome to watch.
This is all about relative velocity. The speed of the ball with respect to the car is 60 mph to the right (negative) and the speed of the car with respect to the ground is 60 mph to the left (positive). This means that the speed of the ball with respect to the ground is 60 mph + (-60 mph) = 0 mph. The math doesn’t seem so complicated, but getting the relative speeds just right isn’t so simple.