1) A skydiver feels weightless while falling and accelerating due to gravity, heavier when the parachute deploys due to increased air resistance, and a normal weight at terminal velocity when acceleration equals zero. 2) Newton's Third Law states that for every action force there is an equal and opposite reaction force. Examples include a hand pushing a wall, which results in the wall pushing back on the hand, or a foot kicking a ball which causes the ball to push back on the foot. 3) Action and reaction forces do not cancel each other out, but rather act on different objects. They can cause motion, such as a swimmer pushing back on water which pushes the swimmer forward, but

1. Warm - Up When does a skydiver feel “weightless?” When the skydiver is falling while accelerating. When does a sky diver feel heavier? When the skydiver’s parachute deploys. When does the skydiver feel normal weight? When the skydiver is at constant (terminal) velocity.

2. Sustained Silent Read Read p. 372 – 377 Write five things that you have learned from the reading.

3. 7-5 – Newton’s 3rd Law Relate the mass of an object to its weight. RelateNewton’s 3 laws to each other. Explain action-reaction forces.

4. Weight vs. Mass The force of gravity is less on the moon then on earth. So a person on the moon would weight less on the moon then on the earth. But their mass is the same!!!! Mass is a measure of the inertia of an object. Weight is a measure of the force of gravity acting on a object.

5. Newton’s Third Law: Action-Reaction Forces For every action, there is an equal and opposite reaction. Hand pushes on the wall, the wall pushes on the hand. Foot kicks the ball, ball applies a force to the foot. Both objects “feel” the force.

6. Key to Action-reaction Pairs Action reaction pairs don’t cancel Action forces act on a different object then the reaction force. Only forces that act on the same object can cancel and result in net force of zero. Action-reaction forces can cause motion. Swimmer pushes back on the water; water pushes forward on swimmer, swimmer moves forward. Not all action-reaction forces cause motion.

7. 7-5 Summary Identify five action reaction pairs.