Newton s laws-class 1-intro

Honors Physics Newton’s Laws

Connection between force & Motion ,[object Object],[object Object],[object Object],[object Object],1. Discuss Aristotle and Galileo’s differing views on the connection between force and motion

Their ideas lead to what we know today as….newton’s laws of motion! ,[object Object],[object Object],Random fact 1…Newton was born on Christmas day! Not so random fact 2… You can also thank Newton for inventing CALCULUS! random fact 3… He was a member of the Parliament of England. Only recorded comments: to complain about a draught in the room and request for a window to be closed. random fact 4… A British psychologist now believes it “fairly certain” that Newton had asperger’s disease. random fact 5… He never married.

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Facts about Force

2. What is Newton’s first law of motion? Provide 3 examples of this law in action.

[object Object],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 EQILIBRIUM ( All the forces cancel out). Newton ’s First Law

[object Object],Newton ’s First Law – The Law of Inertia 3. Define inertia

4. Define mass 5. What is the difference between mass and weight?

[object Object],NOTE: MASS and WEIGHT are NOT the same thing. MASS never changes When an object moves to a different planet. What is the weight of an 85.3-kg person on earth? On Mars (g=3.2 m/s/s)? Weight

Units of mass & force English SI Mass Slug Kilogram (kg) Force Pounds (lb) = 1 slug  foot/sec 2 Newton (N) = kg  meters/sec 2

What forces are acting on you at this moment?

Free body diagrams ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],1. Draw a free-body diagram of this book. 2. What would this FBD look like if someone were pushing the book from the left?

[object Object],W 1 ,Fg 1 or m 1 g ,[object Object],[object Object],[object Object],[object Object],m 2 g T T F N F f Free Body Diagrams

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Newton ’s First Law – The Law of “EQUILIBRIUM”

2. What is Newton’s second law of motion? Give 3 examples of this law in action.

Newton’s second law ,[object Object],DIRECTLY = They do the same thing . If the force increases, the acceleration increases. If the force decreases, the acceleration decreases. Acceleration is inversely proportional to the mass. INVERSELY = They do the opposite. If the mass decreases, the acceleration will increase. If the mass increases, the acceleration will decrease.

[object Object],[object Object],[object Object],[object Object],Newton’s second law If we add a second dog pulling with 100N just like the first dog, we could pull the sled with twice the acceleration, provided the mass of the sled was constant. F(net)=ma 2F=m(2a) 3F=m(3a)

Putting it all together 10 N 3 N Magnitude of F NET = Direction = Acceleration = 7 N RIGHT 10 kg 0.70 m/s/s

N.S.L Tips ,[object Object],[object Object],[object Object],[object Object],[object Object]

Example: applying newton’s 2nd ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],mg F N F a F f Example

[object Object],[object Object],[object Object],mg F N F a F f 30 F ax F ay Example

Example ,[object Object],mg T 1 T 2 T 1 cos19 T 1 sin19 T 2 cos35 T 2 sin35 750 N T 1 = 650 N

Newton ’ s Second Law Honors Physics

N.S.L. ,[object Object],Acceleration is directly proportional to the NET Force. DIRECTLY = They do the same thing. If the force increases, the acceleration increases. If the force decreases, the acceleration decreases. Acceleration is inversely proportional to the mass. INVERSELY = They do the opposite. If the mass decreases, the acceleration will increase. If the mass increases, the acceleration will decrease.

N.S.L. N.S.L. works based on these direct and inverse relationships. As 2 of the variable change, ONE of them must remain constant. If the force is constant, the acceleration and mass change as shown above. F(net)=ma 2F=m(2a) 3F=m(3a) If we add a second dog pulling with 100N just like the first dog, we could pull the sled with twice the acceleration, provided the mass of the sled was constant.

Example ,[object Object],mg T Equation of Motion 21,600 N

Example ,[object Object],50 N 40 N mg F n a 1.23 m/s/s

Example ,[object Object],mg F N T F f  Tcos  Tsin  26.8 N

Newton s laws-class 1-intro

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