Perhaps easier to understand would be:
A racing car on a flat bed trailer of a lorry parked on the level with hand brake off.
Car accelerates as fast as as it can.
Would the lorry move backwards a bit?
Car then brakes or hits the front of the trailer.
Would the lorry move forwards a bit?
So if the lorry was moving, it must have the same effect.
A racing car on a flat bed trailer of a lorry parked on the level with hand brake off.
Car accelerates as fast as as it can.
Would the lorry move backwards a bit?
Car then brakes or hits the front of the trailer.
Would the lorry move forwards a bit?
So if the lorry was moving, it must have the same effect.