This presentation talks about the Newton's Laws of Motion and the early view about it.

1. NEWTON’S LAWS OF
MOTION
Discussants:
Joy U. Fulgar
Jeanelle A. Nevares

2. Sir Isaac Newton
“relations between
the forces acting
on a body and the
motion of the body”

3. INERTIA: The First Law

4. Sir Isaac Newton
Aristotle
Galileo
Copernicus

5. Aristotle on Motion
Aristotle thought of motion in two
terms:
 Natural Motion
 Violent Motion

6. Aristotle on Motion
Natural Motion
Natural motion on Earth was thought to
be either straight up or straight down.
•Objects seek their natural resting
places.
•Heavy things fall and very light things
rise.
•Not caused by forces.

7. Examples
:
•A tree leaf falls to Earth.
•Rain falls to Earth.
•Smoke rises into the air.

8. Violent Motion
Violent motion, on the other hand,
was imposed motion.
•Caused by a push or a pull
•Horse pulling a cart – Ship being
pushed by wind.

9. Aristotle on Motion
Boulders do not
move without cause.
The state of objects was at rest unless they
were being pushed or pulled or move
toward their natural resting place.

10. Copernicus and the Moving Earth
•Copernicus reasoned that the
simplest way to interpret
astronomical observations was to
assume that Earth and the other
planets move around the sun.

11. Galileo on Motion
Galileo’s Idea:
•A moving object needs no force to
keep it moving in the absence of
friction.

12. Galileo on Motion
•Galileo came up with the
definitions of FRICTION.
Friction is the name given to the
force that acts between materials
that touch as they move past each
other.

13. • Balls rolling on
downward-sloping
planes picked up
speed.
• Balls rolling on
upward-sloping planes
lost speed.
Galileo’s Concept of Inertia

14. • A ball rolling on a
smooth horizontal
plane has almost
constant velocity.
Galileo stated that if friction were entirely
absent, a ball moving horizontally would
move forever.
No push or pull would be required to keep it
moving once it is set in motion.

15. Galileo’s Concept of Inertia

16. Galileo’s Concept of Inertia

17. Galileo stated that this tendency of a
moving body to keep moving is
natural and that every material
object resists changes to its state of
motion.
The property of a body to resist
changes to its state of motion is
called inertia.
Galileo’s Concept of Inertia

18. Galileo’s Concept of Inertia
Inertia
•is a property of matter to
resist changes in motion.

19. Think!
A ball is rolled across a counter top
and rolls slowly to a stop. How
would Aristotle interpret this
behavior? How would Galileo
interpret it? How would you
interpret it?

20. •Answer: Aristotle would probably
say that the ball stops because it
its natural state of rest. Galileo
probably say that the friction
the ball and the table overcomes the
ball’s natural tendency to continue
rolling—overcomes the ball’s
and brings it to a stop. Only you can
answer the last question!

21. Newton’s First law of
Motion: INERTIA

22. NEWTON on INERTIA
•An object at rest will stay at
rest, and an object in motion
will stay in motion at constant
velocity, unless acted upon by
an unbalanced force.
**

23. Objects at Rest
-Objects in a state of
rest tend to remain at
rest.
•Only a force will
change that state.

24. Newton’s Law of Inertia

25. Objects in Motion
•Objects in motion tends to keep
on moving, unless acted upon
by an external force.
•In the absence of forces, a
moving object tends to move in
a straight line indefinitely.

26. Inertia on a fast moving vehicle

27. Newton’s Law of Inertia
Think!
A force of gravity between the sun and its
planets holds the planets in orbit around
the sun. If that force of gravity suddenly
disappeared, in what kind of path would
the planets move?

28. Answer: Each planet would
move in a straight line at
constant speed.

29. Mass—A Measure of Inertia
•The more mass an object has, the
greater its inertia and the more
force it takes to change its state
of motion.

30. Mass—A Measure of Inertia
The amount of
inertia an object has
depends on its
mass.

31. Mass Is NotVolume
•Volume is a measure of space and is
measured in units such as cubic
centimeters, cubic meters, and liters.
•Mass is measured in the
fundamental unit of kilograms.

32. Mass Is NotVolume
The pillow has a
larger size (volume)
but a smaller mass
than the battery.

33. Mass Is Not Weight
•Mass is a measure of
the amount of
material in an
object. Weight, on
the other hand, is a
measure of the
gravitational force
acting on the object

34. Mass—A Measure of Inertia
The amount of material in
a particular stone is the
same whether the stone is
located on Earth, on the
moon, or in outer space.

35. Mass—A Measure of Inertia
Mass and weight are proportional to
each other in a given place:
•In the same location, twice the mass
weighs twice as much.
•Mass and weight are proportional to
each other, but they are not equal to
each other.

36. One Kilogram Weighs 10
Newtons
One kilogram of nails
weighs 10 newtons,
which is equal to 2.2
pounds. Away from
Earth’s surface, where
the force of gravity is
less, the bag of nails
weighs less.

37. Think!
Does a 2-kilogram bunch of
bananas have twice as much inertia
as a 1-kilogram loaf of bread? Twice
as much mass? Twice as much
volume? Twice as much weight,
when weighed in the same location?

38. •Answer: Two kilograms of anything has
twice the inertia and twice the mass of
kilogram of anything else. In the same
location, where mass and weight are
proportional, two kilograms of anything
will weigh twice as much as one
of anything. Except for volume, the
answer to all the questions is yes.
Bananas are much more dense than
bread, so two kilograms of bananas
occupy less volume than one kilogram of
bread.

39. The Moving Earth Again
The law of inertia states that
objects in motion remain in
motion if no unbalanced forces
act on them.

40. Arguments:
•Consider a bird sitting at rest in the top of a
tall tree.
•The bird sees a worm, drops down vertically,
and catches it.
•It was argued that this would not be possible
if Earth moved as Copernicus suggested.
•The fact that birds do catch worms from high
tree branches seemed to be clear evidence
that Earth must be at rest.

41. Earth moves at 30 km/s, but so do the tree,
the worm below, and even the air in
between.
Objects on Earth move with Earth as Earth
moves around the sun.
Objects Move With Earth

42. Earth does not need to
be at rest for the bird to
catch the worm.

43. 1. Two thousand years ago, people thought that
Earth did not move. One major reason for
thinking this was that
a.no force was large enough to move the
Earth.
b.Earth’s motion would be unnatural.
c. Earth was near the center of the universe.
d.Earth moved in a perfect circle.
Assessment Questions

44. 1. Two thousand years ago, people thought that
Earth did not move. One major reason for
thinking this was that
a.no force was large enough to move the Earth.
b.Earth’s motion would be unnatural.
c. Earth was near the center of the universe.
d.Earth moved in a perfect circle.
Answer: A

45. 2. According to Aristotle and his followers over
centuries, Earth was at the center of the
universe. The first European to effectively
challenge that notion was
a.Copernicus.
b.Galileo.
c. Newton.
d.Einstein.

46. 2. According to Aristotle and his followers over
centuries, Earth was at the center of the
universe. The first European to effectively
challenge that notion was
a.Copernicus.
b.Galileo.
c. Newton.
d.Einstein.
Answer: A

47. 3. Galileo’s conclusions about motion helped
advance science because they were based
on
a.experiments rather than philosophical
discussions.
b.philosophical discussions rather than
experiments.
c. nonmathematical thinking.
d.Aristotle’s theories of motion.

48. 3. Galileo’s conclusions about motion helped
advance science because they were based on
a.experiments rather than philosophical
discussions.
b.philosophical discussions rather than
experiments.
c. nonmathematical thinking.
d.Aristotle’s theories of motion.
Answer: A

49. 4. If gravity between the sun and Earth suddenly
vanished, Earth would continue moving in
a(n)
a.curved path.
b.straight-line path.
c. outward spiral path.
d.inward spiral path.

50. 4. If gravity between the sun and Earth
suddenly vanished, Earth would continue
moving in a(n)
a.curved path.
b.straight-line path.
c. outward spiral path.
d.inward spiral path.
Answer: B

51. 5. To say that 1 kg of matter weighs 10 N is
to say that 1 kg of matter
a.will weigh 10 N everywhere.
b.has ten times less volume than 10 kg
of matter.
c. has ten times more inertia than 10 kg
of matter.
d.is attracted to Earth with 10 N of
force.

52. 5. To say that 1 kg of matter weighs 10 N is to say
that 1 kg of matter
a.will weigh 10 N everywhere.
b.has ten times less volume than 10 kg of
matter.
c. has ten times more inertia than 10 kg of
matter.
d.is attracted to Earth with 10 N of force.

53. References:
• Newton’s Law. Retrieved from
http://www.physicsclassroom.com/Class/newtlaws/u2l2a.cfm#t
op
• Paul Hewitt. Newton’s First Law of Motion. Conceptual Physics.
Retrieved from
https://is.muni.cz/el/1441/podzim2015/Fy2MP_FBZ/um/worked-
answers-to-hewitt-holiday-sheets.pdf
• The first law of motion. Retrieved from
http://teachertech.rice.edu/Participants/louviere/Newton/law1.h
tml
• NASA Gov. Newton’s First law. Retrieved from
http://teachertech.rice.edu/Participants/louviere/Newton/law1.h
tml