fundamental forces.pdf - Welcome to Physics 101! Lecture...

Welcome to Physics 101!
Welcome to Physics 101!
Lecture 01: Introduction to
Forces
Lecture 01: Introduction to
Forces
Lecture 01: Introduction to
Forces
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Newton’s Laws
Forces
Free Body Diagrams

Newton’s 1
st
Law of Motion Newton’s 1
st
Law of Motion Newton’s 1
st
Law of Motion
Newton’s 1
st
Law of Motion
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If the sum of all external forces on an object is zero,
then its speed and direction will not change. (Know as
the Law of Inertia .)
Example: air hockey table
When the puck travels with no net force on it, it
moves in a straight line with constant speed.
The only time the speed or direction changes is
when a net force (from the walls or mallets) is
exerted on the puck!

Newton’s 2
nd
Law of Motion Newton’s 2
nd
Law of Motion Newton’s 2
nd
Law of Motion
Newton’s 2
nd
Law of Motion
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If a nonzero net force is applied to an object its motion
will change. (The change is described by the equation
F= ma .)
Example: dropping a book
When you drop a Calculus book from your 10
th
story
dorm window, there is a net force acting on it
(gravity) thus it begins to accelerate toward the
street below!