2. Suppose you are at a hockey game when you see a player strike the puck with his stick. As the puck slides across the ice, consider the following: What force causes the puck to start moving? a.The force from the stick. b.The force from the player. c.The force from the ice. d.No force is needed. What force keeps the puck moving as it slides across the ice? a.The force from the stick. b.The force from the player. c.The force from the ice. d.No force is needed.

3. Newton’s First Law can be described using one word: An object at rest will remain at rest. An object in motion will remain in motion, unless acted on by an outside force. Describes what happens when balanced forces act on an object (State of Equilibrium). INERTIA! INERTIA – a quantity of matter, also called MASS. Italian for “LAZY”. Unit for MASS = kilogram.

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5. There are TWO conditions here and one constraint. Condition #1 – The object CAN move but must be at a CONSTANT SPEED Condition #2 – The object is at REST Constraint – As long as the forces are BALANCED!!!!! And if all the forces are balanced the SUM of all the forces is ZERO. The bottom line: There is NO ACCELERATION in this case AND the object must be at EQUILIBRIUM ( All the forces cancel out).

6. If an object is NOT at rest or moving at a constant speed, that means the FORCES are UNBALANCED. One force(s) in a certain direction over power the others. THE OBJECT WILL THEN ACCELERATE.

7. A net force will cause a mass to accelerate. The acceleration of an object is directly proportional to the NET FORCE and inversely proportional to the mass.

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9. Second Law of Motion Continued….a special case! Weight or Force due to Gravity is how your MASS is effected by gravity. NOTE: MASS and WEIGHT are NOT the same thing. MASS never changes. When an object moves to a different planet mass remains the same while weight will change. “g” is the magnitude of the acceleration due to gravity. (9.8m/s 2 )

10. Q:What is the weight of an 85.3-kg person on earth? On Mars where g=3.2 m/s 2 )? What exactly is a Newton? 1 N = 1 kg * 1 m/s 2 On Earth a.85.3 N b.8.70 N c.836 N d.None of the above On Mars a.85.3 N b.273 N c.836 N d.26.7 N

11. Newton’s Third Law For every action there is an EQUAL and OPPOSITE reaction. This law focuses on action/reaction pairs (forces) All you do is SWITCH the wording! PERSON on WALL WALL on PERSON

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