Hey all - this is my first post so I mght as well say hi - I'm not very smart, but find everyday physics interesting. I tried to look up Newton's Laws, but I can't figure out: Is a dirt bike or bicycle a good example of the f=ma principle? All the info I found states that the force is a 'pushing' force, i.e, someone pushing the object. I can see the bicycle with the pedals fitting the explanation, but is a dirtbike an example of this law? Also, is there a name for the point where the wheel pushes off the ground (propulsion? inertia?) Thanks.