1. Homework Read pages 96 – 101 Answer practice problems 15 - 19

2. Newton’s Laws of Motion

3. Newton’s First Law of Motion describes the motion of an object when there is no net force acting on it (net force is zero) referred to as the law of inertia “an object at rest will remain at rest unless acted on by an outside force” “an object that is moving will continue to move in a straight line with constant speed, only if the net force acting on that object is zero”

4. Inertia is the tendency of an object to resist a change in its motion Consider this: Which will have a greater inertia, the 1250 kg object (small car size), or the 68 kg object (~150 pounds)? **Mass is actually a measure of the inertia of an object.

5. Equilibrium An object that has a net force of zero Newtons acting on it This can be inferred from a description of the motion of an object. There are two possible scenarios for objects that are at equilibrium: – At rest, which means not moving (v = 0 m/s) – Moving at a constant velocity (a = 0 m/s 2 )

6. Weight (F g ) Weight is the force exerted by an object as a result of the gravitational force of attraction between two objects F g = mass x gravitational acceleration

7. Practice Problem A rocket has a mass of 2.75 x 10 6 kg. Its engines exert a thrust of +33 x 10 6 N during liftoff. - Determine the weight of the rocket. - Calculate the net force acting on the rocket. - Calculate the acceleration of the rocket. - Determine the velocity of the rocket after 8.0 s.