Force

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Force
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A little History
Isaac Newton was an English physicist/astronomer
among other things and made a number of
significant advances in the study of the world
around us and in space. He was allegedly
struck on the head by
an apple falling from a tree
which
eventually led to his developing his
three laws of motion
now known as Newtons Laws of Motion
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Newtons First Law
Newtons First Law of Motion deals with the
effects of balanced and unbalanced forces.
(Newtons Laws are one of the main reasons that
the units for force are in Newtons) Wording of
Newtons First Law An object in motion will stay
in motion and an object at rest will stay at rest
unless an unbalanced force is acted upon it --
often called the law of inertia
Click here to learn more about inertia
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Inertia
Inertia is the tendency of objects to resist any
change in motion. The amount of inertia that an
object has is directly related to its mass - the
more massive an object is, the more inertia
an object has
Small Inertia
Large Inertia
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Inertia
Think about it like this Which is harder to
get rolling, a train or a Tonka truck?
OR Which would you rather try to stop,
a train moving at 5 km/hr or a Tonka truck moving
at 5 km/hr?
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More Examples Of Inertia
Example 1 When youre riding in a car, and the
car slams on its brakes, your body keeps going
forward until a force acts upon it. Hopefully,
that force is the seat belt. Example
2 Demonstrations in the lab today with coins.
Even though the other coins/index cards moved,
the coin stayed still because no force was acted
upon it
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Newtons First Law
Basically, an object will move at constant
velocity unless an unbalanced force is acted upon
it remember that being stopped (a velocity
of 0 m/s) is still a constant velocity!!!
Click here to learn more about FORCE
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What is this Force thing?
Force the push or pull of one object on
another Force is a vector quantity, therefore,
whenever calculating force, you must give --
an amount -- a unit -- a direction We very
often represent the direction of force with
arrows.
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A glimpse of things to come
Force is a measure of how strong the push or pull
is on one object by another. Think about if you
were pushing on objects in the real world. If
you push with all your might against a small box
full of feathers, you would get it moving faster
than if you pushed with all your might against a
small box full of bricks. Mass, as you will see,
is a factor to consider when we talk about
forces.
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Units for Force
Therefore, while mass is obviously a factor,
speed and acceleration also play a role in
calculating force When reporting force, we use
the units of Newtons (N) 1 N 1 kg m/s2 -- the
units for Newtons are derived from the formula
for force, which we will look at later -- YOU
MUST ALWAYS remember that mass must be in
kilograms (kg) when calculating force The unit
Newton, of course, is named for the famous
scientist Sir Isaac Newton, who spent much of his
time investigating forces
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Types of Forces
There are many different types of forces,
including -- Frictional force (how strong
friction is) -- Gravitational force (weight) --
Torque (perpendicular force) No matter what type
of force you are talking about acting on an
object, that force is either balanced or
unbalanced
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Questions

1. According to Newton, what do objects want to do?
2. Which has more inertia, a walking elephant or an
   eighth grader flying down Broad Street on a bike?

Answer
Maintain their motion stationary objects will
continue to not move and objects in motion will
keep their same velocity until acted upon by a
net force
The elephant has more inertia because it has more
mass. The velocity of an object does not affect
its inertia
Answer
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Questions

• 3. What is a force?
• 4. What is the unit for force and where does it
  come from?

Answer
A force is any push or pull one object exerts on
another
The unit is the Newton (N) and it is made up of
kilograms times meters per second squared
Answer