Physics 10 lecture notes week 2 day 1. Once we think about the causes of motion, we need to consider force. Newton"s first law of motion states that an object in motion will stay in motion but in real life, b/c table has friction, ball rolling on the table will not roll forever. Newton"s second law = where a is nonzero and f is nonzero. Objects in equilibrium: sum of all forces = 0. Blue car will move faster b/c although the forces are equal and opposite, the mass is different because of the weight. Takes a lot of force to expel the gases, the gases push back on the rocket. Rocket launch, the rocket with water launched higher because of its larger mass. On earth, would step on spring scale and the amount of force you pushed down on the spring would cause the spring to push back with a certain amount of force and that is the weight.