1. Newton’s Laws of Motion Mr. Rockensies Regents Physics

2. Newton’s First Law of Motion An object in motion remains in motion unless acted upon by an unbalanced force. Better stated: ◦ If the Net Force is Zero, the velocity remains constant. ◦ If F NET = 0 N velocity is constant

3. Constant Velocity 2 possible velocity conditions v = 0 Static Equilibrium v ≠ 0 Dynamic Equilibrium Both follow the same rules, velocity does NOT change. WHY? Objects naturally resist changes in motion due to their inertia. Inertia = Mass

4. Newton’s 2 nd Law The first Law of Motion looked at examples where there is no Net Force, but what happens when there is one? F NET = ma or a = F NET /m ◦ F NET is the resultant force ◦ Units – 1 N = 1 kgm/s 2 ◦ Direction: F and a have the same direction. Weight = F g = mg, 1 kg = 9.8 N

5. Solving Net Force Problems 1. Identify all Forces 2. Draw free-body diagram 3. Find F NET 4. F NET = ma

6. The Rocket F engine F g = mg F NET = F engine – F g = ma

7. Newton’s Third Law -Action + Reaction For every force exerted on one object by a second object, the second object exerts an equal force, opposite force on the first object. F man on wall F wall on man These forces do not cancel out because they are NOT acting on the same object. This is true for remote forces as well…

8. Earth Moon These forces do not cancel out because they are NOT acting on the same object. This is true for remote forces as well… FgFg FgFg

9. Related Problems