Laws Newton's laws of motion
1 laws 1.1 newton s first law 1.2 newton s second law 1.2.1 impulse 1.2.2 variable-mass systems 1.3 newton s third law laws newton s first law explanation of newton s first law , reference frames (mit course 8.01) the first law states if net force (the vector sum of forces acting on object) zero, velocity of object constant. velocity vector quantity expresses both object s speed , direction of motion; therefore, statement object s velocity constant statement both speed , direction of motion constant. the first law can stated mathematically when mass non-zero constant, as, ∑ f = 0 ⇔ d v d t = 0. {\displaystyle \sum \mathbf {f} =0\;\le...