1 G8 Science Q1- Week 1- Newton_s Law of Motion.ppt

NEWTON’S
LAWS OF
MOTION
PREPARED BY : JOAN I. ATIENZA

S8FE-Ia-15
Investigate the relationship
between the amount of force
applied and the mass of the
object to the amount of change
in the object’s motion

Early Ideas on FORCE &
MOTION
Aristotle
- Believed that a continuous application
of force on a body is required to
produce and maintain the motion of the
body
- The absence of an external force, a
moving body will stop

Once you stop pulling the chair,
it will stay at rest.

Objects continue to move though the force that
started the motion of the body is removed

Galileo
- He disproved the theories made
by Aristotle
- He made an experiments on an
inclined plane & through logical
thinking

h
A
E
D C
Ball rolling down and up inclined planes

Galileo said that the smaller the
inclination of the plane in relation to
the horizontal, the farther the ball
will have to roll to reach the same
height.
He concluded that the smaller the
angle of inclination from the
horizontal the less is the
deceleration of the ball. He
reasoned that if that is the case, the
deceleration becomes zero when the
angle of inclination is zero.

Galileo with his logical mind
concluded that a moving body along
a horizontal frictionless surface does
not require a continuous application
of force to maintain its uniform
velocity.

ISAAC NEWTON
 Sir Isaac Newton was one of the
greatest scientists and mathematicians
that ever lived. He was born in England
on December 25, 1643. He was born
the same year that Galileo died. He
lived for 85 years.

He was interested in
experimental science thus his
studies restated the idea of
Galileo and came up with the
Law of Inertia

First Law :
LAW OF INERTIA
INERTIA
- A property of a body to resist changes
in its motion
- It is equal to the mass of the body

LAW OF INERTIA
 An object at rest will remain at rest unless
acted on by an unbalanced force. An object
in motion continues in motion with the same
speed and in the same direction unless acted
upon by an unbalanced force.

What does this mean?
This means that there is a natural
tendency of objects to keep on
doing what they're doing. All
objects resist changes in their state
of motion. In the absence of an
unbalanced force, an object in
motion will maintain this state of
motion.

This law is the same reason why you
should always wear your seatbelt.

Second Law:
LAW OF ACCELERATION
Acceleration is produced when a
force acts on a mass. The greater
the mass (of the object being
accelerated) the greater the
amount of force needed (to
accelerate the object).

 Everyone unconsciously knows the
Second Law. Everyone knows that
heavier objects require more force to
move the same distance as lighter
objects.

 However, the Second Law gives us an
exact relationship between force, mass,
and acceleration. It can be expressed as
a mathematical equation:

example of how Newton's Second
Law works

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.

Third Law:
LAW OF ACTION AND REACTION
For every action there is an equal
and opposite reaction.

 This means that for every force there is a
reaction force that is equal in size, but
opposite in direction. That is to say that
whenever an object pushes another object it
gets pushed back in the opposite direction
equally hard.

Let's study how a rocket works to
understand
Newton's Third Law.
 The rocket's action is to push down on
the ground with the force of its
powerful engines, and the reaction is
that the ground pushes the rocket
upwards with an equal force.

The rocket is pushing
the ground
Pushes the
rocket upward by
the ground with
equal force

PRACTICE TEST
The tendency of an object to resist change in its motion is known
as
a. Mass b. Inertia c. Force d. Motion
A net force (an unbalanced force that changes motion) causes an
object to
a. stay at the same speed. b. not move. c. Accelerate or
decelerate d. None of these
Forces that are equal in magnitude and opposite in direction are
known as
a. balanced forces b. net forces c. friction forces d. None of
these

 Two boys wearing in-line skates are standing on a
smooth surface with the palms of their hands
touching and their arms bent, as shown above. If
Boy X pushes by straightening his arms out while
Boy Y holds his arms in the original position, what
is the motion of the two boys?

 a. Boy X does not move and Boy Y moves
backward.
 b. Boy Y does not move and Boy X moves
backward.
 c. Boy X and Boy Y both move backward. The
motion depends on how hard Boy X pushes.
 d. Both will not move.

In science, a push or a pull of an object is called a(n)
a. force. b. acceleration. c. inertia. d. friction
You are riding fast on a skateboard when your wheel
suddenly gets stuck in a crack on the sidewalk. Why
does your body go flying forward?
a. there is a net force pushing you off your skateboard
b. your inertia keeps you moving forward
c. someone pushed you
d. none of these

The force that pulls falling objects toward Earth is called
a. Gravity b. Free fall c. Inertia d. Acceleration
According to Newton’s third law of motion, when a hammer
strikes and exerts force on a nail, the nail
a. creates a friction with the hammer.
b. disappears into the wood.
c. exerts an equal force back on the hammer.
d. Nothing will happen

“However difficult life may seem, there
is always something you can do and
succeed at.”
― STEPHEN HAWKING

1 G8 Science Q1- Week 1- Newton_s Law of Motion.ppt

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