I apologize if this seems much too "freshman", and may come across as annoyingly simple to some more trained or educated on this board. However I will ask the question anyways as I have failed to find an answer elsewhere. Under Newton's Second Law of Motion, f=ma. thus F = kg (m/s^2) But when a person pushes against a wall like in the picture below, there is no acceleration, a=0. The person and the wall have 0 velocity and 0 acceleration. If a=0 then F=m(0), F=0 How can there be no force here (treating it mathematically according to the formula), when the person is exerting a force upon a body(the wall)? --- And secondly, if an object of a certain mass and velocity, is in motion but not accelerating, Newtons second law also would calculate that there is no force according to the formula. Say a 4 kg bicycle moving at a consistent velocity of 2 m/s, that has 0 acceleration. http://www.theglobalintelligencer.com/images/bicycle.jpg F=(4kg)(0) = 0 I know the momentum p, would equal p=(4kg)(2m/s) from p=mv. But there is no momentum without a force being exerted upon the object. Force is coming from the rotation of the tire via the humans legs rotating a gear (translating an general up and down "force" into a rotational "force", giving the bicycle (the object) a momentum.