This document discusses Newton's laws of motion. It defines key terms like mass, inertia, weight, force, and acceleration. It explains Newton's three laws: 1) an object remains at rest or in motion unless acted on by an external force, 2) acceleration is directly proportional to force and inversely proportional to mass, and 3) for every action there is an equal and opposite reaction. Examples are provided to illustrate applications of Newton's laws, like calculating weight, acceleration, and tension in ropes. Formulas for force, acceleration, and other concepts are defined.

1. Chapter 4-6 Newton’s Laws of Motion
Mrs. Pagar
• Gravity is a very important force in nature, it literally holds
the universe together. Yet it is also one of the weakest force
in nature.
• I Corinthians 1:27 “ But God hath chosen the foolish things
of the world to confound the wise; and God hath chosen the
weak things of the world to confound the things that are
mighty.”
• Though we are weak, God can do mighty things with us.
Perhaps the greatest power in the universe in manifested
when a Christian who loves God with all of his/her heart
shares burdens with the Lord in prayer. What appears to be
weak and foolish has a greater influence than the most
powerful physical agents in the universe.

2. Mass• Mass
• -amount of matter in an object.
• It is measured in kilograms.
• It is a measure of the inertia of an object.
• Inertia
• is the natural tendency of a body to resist
changes in motion. It is the reluctance of any
material object has to change in its state of
motion.

3. • Weight
• -gravitational force acting on the object.
• It depends on the location of the object.
• Unit: Newton

4. History
• Aristotle
• - foremost Greek scientist, studied motion and
divided it into natural motion and violent
motion.
• Natural motion-straight up, down, circular
motion.
• Violent motion-imposed motion, with an
external cause

5. • Nicolaus Copernicus(1473-1543)
• First person to publicly state that the earth
revolves around the sun.
• It was extremely controversial at the time. He
worked in secret to escape persecution. His
printed work,De Revolutionibus reached him
on the day of his death.

6. • Galileo Galilei
• Foremost Scientist of late-Rennaisance Italy,
supported Copernicus theory
• -demolished the notion that a force is
necessary to keep an object moving.
• He found that a ball rolling down one inclined
plane would roll to nearly the same height as
where it originally started.

7. • 1st Law of Motion :
• An object remains at a constant
speed in a straight path until a net
force acts on it.
NEWTON’s LAWS

8. Newton’s First Law
• Law of Inertia
• “A body remains at rest or
moves in a straight line at a
constant speed unless acted
upon by a force.”

9. Force
• …the agency of change.
• … a push or a pull.
• …changes the velocity.
• …is a vector quantity.
• ...measured in Newton’s.

10. NEWTON’s
2nd Law of Motion : F = m•a
acceleration of the club
force of the club
mass of the club

11. Forceof gravity
Force of muscles
Net force
•Net forceis the total amount of Force
(minus the forces that cancel each other
out).

12. • Net force
• -vector sum of all forces acting on an object;
affects the object’s state of motion.
• When an object is at rest, its weight is
balanced by an equal and opposite support
force.
• An object is in equilibrium when it is at rest,
with zero net force acting on it.

13. • Newton’s 2nd Law:
• The acceleration produced by a net force on
an object is directly proportional to the
magnitude of the net force, is in the same
direction as the net force, and is inversely
proportional to the mass of the object
• F=ma
• Newton(N)- unit of force

14. Newton’s Second Law
The Sum of the Forces acting
on a body is proportional to
the acceleration that the body
experiences
F  a
 F = (mass) a

15. amF


xx maF 
yy maF 
Net Force
zz maF 

16. • F = ma
• a=F/m
• a=acceleration : m/s 2
• m= mass of the object : kg
• F=force:N
• The acceleration is proportional to the Force
• The acceleration is inversely proportional to
the mass of the object
• Acceleration is in the same direction as the
net force.

17. When the net force is Zero.
-> NO movement
When the net force is NOT Zero.
-> movement

18. • Pressure
• -force per unit area
• P=F/A
• Unit is Pascal
• 1 Pascal= 1 N/m 2
• The bigger the force, the bigger the pressure.
• The smaller the area, the bigger the pressure

19. • The acceleration of all objects in free fall is the
same, regardless of their mass. a=g=9.8 m.s.s
• When air resistance is present, a falling object
accelerates(increase in speed) only until it
reaches its terminal speed
• (constant speed where air resistance balances
the force of gravity).

20. • NEWTON’s 3rd Law of Motion:
• For everyaction thereis anequal and
opposite reaction.

21. NEWTON’s
3rd Law of Motion:
For everyaction,there is
an equaland oppositereaction.

23. • An interaction between two things produces a
pair of forces.
• Interacting things exert forces on each other.
• The two interacting forces are equal in
strength and opposite in direction.
• Forces always occur in
• pairs.

24. • Things fall toward the ground because the
earth attracts objects towards itself. This
attraction is called the earth’s
• Gravity
• All objects in the universe attract each other.
• The more massive the object, the greater the
attraction
• These attractions are called action-at-a-
distance forces because they act on objects
without touching them.

25. • Weight
• - measure of the force of gravity
• W=mg g= 10 m/s2
• 1 kg=2.2 lb
• If you are 120 lb, 120 /2.2= 55 kg
• m = 55 kg
• W= mg = 55 ( 10)= 550 N

26. Tension
(Tensile Force)
• Tension
• is the force in a string, chain or tendon that
is applied tending to stretch it.
• FT
• Example: A 20 N picture frame hangs
supported by 2 strands of rope. How much
force is supported by each strand?
• Answer : 10 N

27. Normal Force
• The normal force on an object that is being
supported by a surface is the component of
the supporting force that is perpendicular
to the surface.
• FN

28. Coefficient of Friction
Kinetic Friction
• Ff = mk FN
• Static Friction
• Ff  ms FN
• In most cases, mk < ms.

29. #21 p. 57 Conceptual Physics
• If a woman has a mass of 50 kg, calculate her
weight in Newtons.
• Problem: Fg=?
• Given: m= 50 kg; g = 10 m/s2
• Formula: F= ma; a= g; Fg =mg
• Solution: Fg = mg
•Fg =(50)(10)
•Fg = 500 N
• Final Answer: Fg =500 N

30. #19 p. 72 Conceptual Physics
• Calculate the acceleration of a 2000 kg single-engine
airplane just before takeoff when the thrust of its
engine is 500 N.
• Problem: a=?
• Given: m= 2000 kg ; F= 500 N
• Formula: F =ma ; a=F/m
• Solution: a=F/m
• a=500/2000
• a= 0.25 m/s2
• Final answer: a= 0.25 m/s2