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Forces
Science of Technology
© 2011 Project Lead The Way, Inc.
Force
The amount of force acting on an object can
be determined if you know the distance
traveled and the elapsed time. Data collected
from trials is used to calculate velocity and
acceleration.
Gravity
Sir Isaac Newton was a great
scientist who is credited for
discovering gravity.
• One day Newton was sitting in
an orchard under an apple tree
and noticed apples falling to the
ground. Maybe an apple hit him
on the head; maybe it didn’t. Like
all good scientists, Newton
collected and examined the data
(the apple) and ate it.
•
Why?
Like all good scientists, Newton
asked the question why? Why did
the apple fall toward the ground
instead of toward the sky? From
this question Newton developed
the Law of Gravity.
Newton’s Law of Gravity
• Gravity is the natural force that pulls one object
toward another. The strength of this pull depends on the
mass of the objects involved.
• The pull is directly proportional to
the masses of the objects and
inversely proportional to the
distance between the objects.
• Because the earth is so large, objects
are pulled toward its center instead of
each other. This pull of gravity is what gives us weight
and allows us to walk around without flying into space.
Newton’s Laws
After developing the law of gravity, Newton
continued to work with objects of matter to
determine how they react with each other.
This work led him to the development of
what is now called
Newton’s 3 Laws of Motion
Newton’s First Law of Motion
The Law of Inertia
Objects at rest stay at rest unless acted upon by
an unbalanced force. Objects in motion stay in
motion in a straight line and at a constant speed
unless acted upon by an unbalanced force.
Example: Cue ball striking
a set of billiard balls
Newton’s Second Law of Motion
The Law of Acceleration
Objects acted upon by an unbalanced force accelerate in
the direction of the force directly proportional to the
magnitude of the force and inversely proportional to the
mass of the object.
Example: Soccer ball
that is passed and
kicked into a goal by
another player
Newton’s Third Law of Motion
The Law of Action and Reaction
For every action by a force, there is an equal and
opposite reaction by a different force.
Example: Batter
striking a ball
that is pitched
and hitting a
home run
Force
• Force is the push or pull exerted on an object.
• The magnitude of a force can be found by
multiplying the mass and the acceleration of the
object.
• Force equals mass times acceleration.
F = ma
Image Resources
Microsoft, Inc. (2009). Clip Art. Retrieved January 30, 2009, from
http://office.microsoft.com/en-us/clipart/default.aspx