Transcript Newton`s Laws of Motion

What are
Newton’s
Laws of Motion?
I. Law of Inertia
II. F=ma
III. Action-Reaction
1st Law of Motion
(Law of Inertia)
An object at rest remains at
rest, and an object in motion
remains in motion at constant
speed and in a straight line
unless acted on by an
unbalanced force.
1st Law



Inertia is the
tendency of an object
to resist changes in
its velocity: whether
in motion or
motionless.
More mass = more
inertia
This law is
nicknamed the law of
inertia
These pumpkins will not move unless acted on
by an unbalanced force.
1st Law

Example:
A
golf ball will sit on the tee until acted upon by an
outside force.
 Once hit, it will travel until fluid friction and gravity
slow it down.
 IF…their was no atmosphere or gravity to slow it
down it would continue on forever in the direction it
was hit.
In your words…
without peeking!!!
Write out Newton’s first law
What is Newton’s first law’s nickname?
What is this unbalanced force that
acts on an object in motion?

Four main types of friction:
1.
2.
3.
4.
Sliding friction: ice skating
Rolling friction: bowling
Fluid friction (air or liquid): air or water resistance
Static friction: initial friction when moving an object
Using only your school supplies…
demonstrate each of the four types of
friction with your neighbor.
Sliding friction:
Rolling friction:
Fluid friction:
Static friction:
Newtons’s 1st Law and You
Because of inertia, objects resist changes in their
motion. When the car going 80 km/hour is
stopped by the brick wall, your body keeps
moving at 80 m/hour until friction and gravity
slow it down and stop it.
Talk it out…
4 types of Friction
2 parts of
Newton’s first law
Share one real
world example.
2nd Law
2nd Law
The acceleration of an
object depends on the mass of
the object and the amount of
force applied.
2nd Law

Units:
 Force:
Newton (N) or kg m/s/s
 Mass: kilograms (kg)
 Acceleration: meters per second per second
(m/s/s)

One Newton = force required to accelerate
one kg of mass at one m/s/s.
2nd Law (F = m x a)
How much force is needed to accelerate a
1400 kilogram car 2 meters per
second/per second?
 Write the formula
F=mxa
 Fill in given numbers and units
 F = 1400 kg x 2 meters per second/second
 Solve for the unknown


2800 kg*m/s/s or 2800
N
Think… Pair… Write… Share

If I drop two objects of different masses at
the same time which will hit the floor first?
The lighter or the heavier one?

If I drop two objects with the same mass,
but different shapes which will hit the floor
first? The smaller or larger object?
Newton’s 2nd Law proves that
different masses accelerate to the
earth with different forces, but at the
same rate.
1.
2.
3.
Due to gravity, all objects accelerate
towards earth at 9.8 m/s/s.
Objects with different masses accelerate to
the ground at the same rate.
However, the greater the mass is the greater
their impact is on Earth.
A
B
C
If mass remains constant, doubling the acceleration, doubles the force. If force remains
constant, doubling the mass, halves the acceleration.
4 type of
forces
Gravity
 Electricity
 Magnetism
 friction

Check
YourwillUnderstanding
1. What acceleration
result when a 12 N net force
applied to a 3 kg object?
12 N = 3 kg x 4 m/s/s
2. A net force of 16 N causes a mass to accelerate at a
rate of 4 m/s/s. Determine the mass.
16 N = 4 kg x 4 m/s/s
3. How much force is needed to accelerate a 66 kg skier 2
m/sec/sec?
132 N = 66 kg x 2 m/s/s
4. What is the force on a 1000 kg elevator that is falling
freely at 9.8 m/sec/sec?
9800 N = 1000 kg x 9.8 m/s/s
Talk it out…
What measurements
must we know or seek
nd
out in Newton’s 2
law?
4 types of forces
3rd Law
Whenever
one object exerts
a force on a second object,
the second object exerts an
equal and opposite force on
the first.
3rd Law
Think of one thing you are applying a force to at the
current moment that is applying a force back.
According to Newton, whenever objects
A and B interact with each other, they
exert forces upon each other.
3rd Law
There are two forces
resulting from this
interaction - a force
on the chair and a
force on your body.
These two forces are
called action and
reaction forces.

Newton’s
Examples:
 Fish
3rd Law in Nature
propelling through
the water (force on water
is backward and the fish
moves forward)
 Stepping out of a boat
onto the dock and boat
moves away from the
dock (person moves
forward, boat moves
backward)
 Birds push down on the
atmosphere and the air
lifts them so they can to
stay aloft
3rd Law
Explain in a sentence
what the action /
reaction pair is in
the scenario to the
left at take-off.