There's a problem going round in my mind that i'm not realy sure it's possible to put forward in a way that will make sense, possibly because i have trouble defining the real point myself, but here goes. It's a very simple thing. Take any object travelling or at rest and change it's velocity, the method to do so isn't important. Fine as it goes, but the problem I have is defining how this actually happens, due to what seems to me to be a bit of a paradox. An object, any object, cannot simply go from velocity A to velocity B, to do so would require an instantaneous change in velocity which in turn would require an infinite force.So now matter how small you make the gap between "A" and "B", no object (with mass) can ever be said to change from velocity A to velocity B. So how does anything ever change velocity?!!. I'm sure there's a very obvious explanation that i'm just missing but this has been going around in my mind for months without a solution!