I got a 30kg rock in space, no gravity, no friction. It is traveling at a CONSTANT speed of 100m/s. According Newton's second law, There should be NO force because there is NO acceleration. But I know if it hits another object it will either move the object or put a hole in it so I know there is force there but according to F=ma there is no force. How do I calculate the force? Please, I am not taking physics, so I am learning this on my own. So please try to put this in words a layman can understand.