1. Newton's Three Laws of Motionby
BUENO OLIVIER

2. Isaac Newton (1642-1727) Life & Character
Born at Woolsthorpe in Lincolnshire (England)
entered Cambridge University in 1661
Professor of Mathematics in 1669 and Natural Philosopher
President of the Royal Society of London in 1703 until death.

3. Scientific achievements
OPTICS
discovered measurable, mathematical patterns in the phenomenon of color, found white light as mixture of infinitely varied colored rays,…book: Opticks (1692).
MATHEMATICS  
discovered general methods of resolving problems of curvature, embraced in his "method of fluxions" and "inverse method of fluxions",..books: Principia I and II (1687)

4. Scientific achievements
GRAVITATION
calculated the relative masses of heavenly bodies from their gravitational forces, calculated the force needed to hold the Moon in its orbit book: Principia I and III (1687)
MECHANICS
calculated the centripetal force needed to hold a stone in a sling, and the relation between the length of a pendulum and the time of its swing book: Principia I (1687)

5. Newton’s First law of motion
Also known as law of inertia,
States,
An object will remain at rest, or uniform motion in a straight line, with the same speed and in the same direction unless acted upon by an unbalanced force.

6. Newton’s First law of motion
Comments
This means that if you leave a book on a bench over night, when you return in the morning, unless an outside force moved it, it will be in the same place
No external forces applied-> the book remains at rest

7. Newton’s First law of motion
Comments & Examples
But what is an unbalanced force? first consider a book at rest on a bench. There are two forces acting upon the book. - the Earth's gravitational force, and the push of the bench on the book (sometimes referred to as a Fn). Since these two forces are of equal magnitude and in opposite directions, they balance each other. The book is said to be at equilibrium.
The bench pushes upward on the book
Gravity pulls downward on the book

8. Newton’s First law of motion
Comments & Examples
Consider another example of a balanced force. There are two forces acting upon this person; The force of gravity and the force of the floor. these two forces are equal magnitude and in opposite directions, The person is at equilibrium.
The floor pushes upward on the person
Gravity pulls downward on the person

9. Newton’s First law of motion Involving Friction
Comments & Examples
Now consider a book sliding from right to left across a bench. Sometime in the prior history of the book, it may have been given a shove. The force of gravity and the force of the bench on the book balance each other. Yet there is no force present to balance the force of friction. As the book moves to the left, friction acts to the right to slow the book down. There is an unbalanced force. The book is not at equilibrium and subsequently accelerates
The bench pushes upward on the book
Force of friction between the bench/book
Gravity pulls downward on the book

10. Newton’s First law of motion Involving Friction
Let’s exercise
Consider that the book weighs 0.2 kg. As it slides across the bench with a constant velocity, its coefficient of friction is What force must be exerted on the book, so that it maintains its constant velocity? (go to the next slide for the answer) Fn
Fob = ?
Ffr Fg

11. Newton’s First law of motion Involving Friction
Answer & explanations
We know that the magnitude of the force of gravity is mg. We recognize that the two object in contact are in relative motion (kinetic friction = Ffr = μkFn).
Solving with the y-direction equation gives Fn = mg, and solving for the x-direction, F = μkmg)
The force that must be used on the book is F = μkmg = (0.2)(0.15)(9.80 m/s) = N

12. Newton’s First law of motion
Comments & Examples
Considering a soccer ball in the middle of a field with no external forces exerted (kicking, moving, high winds,…) on it.
Normal force of the ground on the ball
No external forces
Consider that the book weighs 2 kg. As it slides accros the bench with a constant velocity, its coefficient of friction is What force must be exerted on the book, so that it maintains its constant velocity?
Force of gravity on the ball

13. Newton’s First Law of Motion
The floor pushes upward on the person
Comments & Examples
If you kick the soccer ball, it will continue moving until it hits something.Newton’s First Law of Motion Fn
Comments & Examples
This also means that if you kick a soccer ball, it will continue moving until it hits something. However, the ball will eventually stop even if it does not hit a wall (the friction between the ball and the ground, and between the ball and the air). Fg
Gravity pulls downward on the person

14. Newton’s First Law of Motion
The floor pushes upward on the person
Comments & Examples
Your foot can only interact with the ball through forces of contact (there is a gravitational force between your foot and the ball, but it is so tiny that it is completely negligible), so once the ball is not in contact with your foot, it no longer exerts any force on the ball. Fn
Comments & Examples
This also means that if you kick a soccer ball, it will continue moving until it hits something. However, the ball will eventually stop even if it does not hit a wall (the friction between the ball and the ground, and between the ball and the air).
Force of contact between the foot and the ball Fg
Gravity pulls downward on the person

15. Newton’s First law of motion involving Friction
Comments & Examples
Once the ball is not in contact with the foot, the only object interacting with the ball is the ground. The ball will eventually stop even if it does not hit a wall (the friction between the ball and the ground, and between the ball and the air)Newton’s First law of motion Fn Fn Fg
Friction between the ball and the air
Ffr Fg

16. Newton’s First law of motion
Comments & Examples
We feel the effects of Newton's First Law every day, but usually don't notice them because other forces interfere. If it was not for other forces we will be in constant motion.

17. Newton’s First law of motion
Comments & Examples
On earth, the atmosphere will eventually slow down all moving objects, but in a vacuum (basically an empty space with no air or atmosphere), like space, it will be more obvious that objects obey Newton's Laws.
Direction of the force due to the reactors
Friction between the wind and the plane
Direction of the force from the reactors Fg

18. Newton’s First law of motion
Comments & Examples
In space, the First Law is much more obvious. Objects will follow their natural trajectories until they are stopped by an outside force.

19. Newton’s First law of motion
Comments & Examples
One of the most common places people feel the First Law is in a fast moving vehicle, such as a car or a bus, that comes to a stop. An outside force stops the vehicle, but the passengers, who have been moving at a high speed, are not stopped and continue to move at the same speed

20. Newton’s First law of motion
Comments & Examples
If the car hits a cement road divider it is stopped (outside force). The crash dummy, however is not so lucky. Since he is not wearing a seat belt, and is not connected to the car, he will continue to move at 60 mph, flying out through the front windshield.

21. Newton’s First Law of Motion
Comments & Examples
The dummy will fly through the air until he hits the ground. This is because the earth's gravity stopped him from moving any further. If this collision had happened in zero-g, in a vacuum, the dummy would theoretically keep on hurtling away from the car at 60 mph.

22. Newton’s Second law of motion
States,
The acceleration of an object is directly proportional to the net force acting on it and is inversely proportional to its mass.
The direction of the acceleration is in the direction of the net force acting on the object

23. Newton’s Second law of motion
shortened => ΣF = ma
where f is a push or pull that gives energy to an object the motion of the object. a is the rate of change of velocity.

24. Newton’s Second law of motion
Heavy mass, needs more force
Comment & Example
Newton's Second Law is more abstract than the first. The greater the mass, the greater the amount of force needed to accelerate the object.
Mike's car, which weighs 1,000 kg, is out of gas. Mike is trying to push the car to a gas station, and he makes the car go 0.05 m/s/s. Using Newton's Second Law, you can compute how much force Mike is applying to the car. Now that you are
Small mass, needs less force

25. Newton’s Second law of motion
Example:
Betty is developing her muscles by pushing this car that weighs 1500 kg. She makes it go 0.02 m/s/s. Using Newton's Second Law, can you compute how much force I applied to the car? (the answer in the next slide)
Not really who you expect to push the car !!!
Force exerted by the ground on the car
F = mass car x g

26. Newton’s Second law of motionFn
30 Newton applied Fg
Comments & Examples
Betty has not really move that much consider she has only exerted 30 Newton of force. (F=MA, so you plug in the data and get F = 1500kg x .02 m/s/s. This comes out to 30 kg m/s/s, which is equal to 30 Newton.

27. Newton’s Second law of motion
Example:
Here Betty is trying to do the impossible. She wants to push this 2500 kg van to a gas station. She computes 125 Newton on the car. How fast will she make it go?
She’s trying hard !!!
Force exerted by the ground on the car
Statement
Anytime an object exerts a force on another object, the second object exerts an equal and opposite force on the first.
125 N
A = ?
F = 2500 x g

28. Newton’s Second law of motionFn
125 N
0.05 m/s/s Fg
Answer & Explanations
It may seem impossible but Betty will make it go 0.5 m/s/s. Because using Newton's Second Law, we found that… (F=MA, => A=F/M. So you plug in the data and get A = 125/2500kg. This comes out to 0.05 m/s/s.

29. Newton’s Third law of motion
Comments:
Anytime an object exerts a force on another object, the second object exerts an equal and opposite force on the first.

30. Newton’s Third law of motion
Comments
Newton's Third Law is probably the most famous of his laws.
The Third Law at first seems simple, but is a very important law.
Every time we interact with our surroundings we feel the Third Law.

31. Newton’s Third law of motion
Comments & Examples
If use the convention that F means the force on object A from object B, then Newton's third law can be written
FAB = - FBA
Object A
Object B

32. Newton’s Third law of motion
Comments & Examples:
When you punch someone in his face your hand not only applies a force to the person's face, the person's face applies a force to your hand.
Force exerted on his face by the punch
Force exerted on the hand by his face

33. Newton’s Third law of motion
Comments & Examples
The magnitude of the force on each body is identical and the forces on the on the two bodies are in the opposite directions to each other.
Ffp
-Fpf

34. Newton’s Third law of motion
Comments & Examples:
The only reason why a rocket is able to launch, is that when its engine pushes out the gases, the gases exert an equal and opposite force back on the rocket, which accelerate.
Force exerted on the rocket by the engine
Force exerted on the engine by the rocket

35. Newton’s Third law of motion
Comments & Examples:
One of the most unnoticeable Newton’s third law, is when we walk.
We can walk forward because, when one foot pushes backward against the ground, the ground pushes forward on that foot.
Force exerted on her foot by the floor
Force exerted on the floor by her foot

36. Newton’s Third law of motion
The floor pushes upward on the person
Comments & Examples:
Newton first law still applying in this case.
Her mass has also in influence on her walking.
Force exerted on her foot by the floor
Force exerted on the floor by her foot
Gravity pulls downward on the person

37. Newton’s Third law of motion
Comments & Examples:
Even in the most unthinkable moment, we do exert Newton’s third law.
We cannot be touched without being touched

38. presented by BUENO OLIVIER
The End
presented by
BUENO OLIVIER