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Sir Isaac
Newton was a
17
th
century
British
scientist. He is
best known for
his three laws
of motion.

Forces and Newtons Laws

A force is any push or pull that can move an object. There are many types of forces
in the universe. To make something move, a force must be applied. Earth has many
forces that work against moving an object.

Gravity is a force that is constantly pulling down on objects on Earth. Sir Isaac
Newton was the first person to describe gravity. He noticed that when a ball is thrown in
the air, it would fall down. This happens because of gravity.

Friction is the force that works against motion. A box sliding across the ground has
difficulty moving. This difficulty occurs because gravity is pushing down and friction is
pushing in the opposite direction. Friction can cause heat. If you rub your hands
together while pressing tightly, your hands will begin to heat up.

Air resistance is a force from air that also affects motion. When air is
pushed against an object, the object will slow down. Imagine a person
falling jumping from an airplane. If the person does not have a parachute, the
person will fall very quickly. If the person has a parachute and opens it, the
air will push against him or her or her, slowing the fall so he or she will land
safely.

Aerodynamics is a type of engineering that looks at shapes that the air
will affect the least. This reduces the air resistance on the object.
When this occurs, it is said that that the object is a aerodynamic.
School buses are big and rectangular. They are not designed to go
fast. A school bus is not aerodynamic. A racecar is small and close to
the ground. Some racecars even have wings. A racecar is designed to cut through the
air so it can go faster. A racecar is aerodynamic. Cars that most people drive are not
aerodynamic. Compare the shape and design of the average car and a sports car and
see which is more aerodynamic.
A racecar has to be
aerodynamic to go fast.

Sir Isaac Newton was a genius. He questioned the simple things. He would ask,
Why does this happen? or Why does an apple fall from a tree? His answer became
The Law of Universal Gravitation. This law states that every object in the universe is
attracted to every other object in the universe. This means that objects that have mass
also have gravity. The Earth makes an apple fall to the ground because the Earth has
much more mass than the apple; therefore, the apple is attracted to the Earth more than
the Earth is attracted to the apple. Newton also developed three laws of motion.

Newtons 1
st
Law of Motion states that every object in motion will
stay in motion and every object at rest will remain at rest until an
outside force acts on the object. This is known as inertia. An
example of this occurs when a football is thrown. The forces acting
on the football are air resistance (also friction from the air) and gravity. If these forces
were not there to slow the football, the football would keep going, because in space
there is little gravity and no air resistance.

Newtons 2
nd
Law of Motion states that all objects in motion can be broken down into
an equation; force equals mass times acceleration or F=ma. This law states that the
force needed to move an object is related to the mass of the object and the acceleration
of the object. If the force of an object that is moving is increased then the acceleration
will also be increased.

Newtons 3
rd
Law of Motion states that for every action there is an
equal and opposite reaction. An example of this is how a rocket works.
For a rocket to go up into space, rocket fuel is needed. When the rocket
fuel is ignited, the gases burn quickly and leave the bottom of the rocket.
The gases push down making the rocket go up. The action of the gases
pushing down are equal and the opposite reaction is that the rocket
goes up.
o up.
The gases
escaping from
the shuttle
make it g

There is a science known as physics. Physics is used to study where the stars
are in the sky and how to plot the path that the space shuttle will follow into space.
Physics combines all of the laws of motion and then uses these forces to explain how
something will move because of these forces. Understanding physics requires
understanding velocity. The velocity of something says how many meters something is
moving over time and in what direction it is moving. Velocity is similar to speed. If a car
is traveling 70 kilometers an hour, in science it would be written 70 km/hr. The car is
traveling this speed, or velocity. Physics shows how objects react when they meet each
other.






















I.
Sir Isaac Newton was a 17
th
century British scientist who explained the laws
of motion.
A. Newtons Laws
1. Newtons 1
st
Law of Motion states that an object in motion will
remain in motion and an object at rest will remain at rest until an
outside force acts on the object.


2. Newtons 2
nd
Law of Motion states that the force needed to move an
object is related to the mass and acceleration of the object.
a. Simply stated by the equation: F=ma.
b. If an objects acceleration is desired more force is needed to
accomplish this.




3. Newtons 3
rd
Law of Motion states for every motion there is an equal
and opposite reaction.
a. An example of this would be the gas escaping goes down
while the rocket goes up into the sky.

B. The Law of Universal Gravitation is not a law of motion but another law
that Newton stated.
a. All objects in the universe are attracted to all the other objects
in the universe by the force of gravity.

II.
There are many types of natural forces that try to stop motion. Some
examples are: air resistance, friction, and gravity.

III. How do objects move?
1. Velocity is the speed of an object in a direction.
2. Aerodynamics is a type of engineering that studies how to reduce air
resistance by changing the shape of the vehicle.




















ENGLISH

SPANISH

HAITIAN
CREOLE

PORTUGUESE


Force



Gravity



Friction



Air Resistance



Aerodynamics



Law of Universal Gravitation



Newtons 1
st
Law of Motion



Inertia



Newtons 2
nd
Law of Motion



Newtons 2
nd
Law of Motion



Newtons 3
rd
Law of Motion



F=ma



Action



Reaction



Opposite



Velocity



Direction