Download Introduction to Forces Guided Notes

Introduction to Forces Guided Notes
Name:____________________ Class:________
Forces throughout History
_________________________ (384-322 BC) believed that
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

heavenly bodies (sun, moon, etc.) had circular motion
all earthly things had natural ‘resting places’ that they would return to
motion of earthly things was ‘violent motion’ that had external causes (being pushed or pulled)
For 2000 years after Aristotle, it was thought:
• Movement is against nature state
• No Force = no movement
In the 16th c. ________________________________ secretly developed his heliocentric theory – the theory that the
Earth and planets orbit the sun. Knowing it would be controversial, he published it only shortly before his death.
In 17th c. ____________________________ also theorized that force is NOT needed to keep an object in the motion
(straight-line, constant speed). Instead, he believed forces change motion.
Every object resists change to its state of motion/velocity. To change it, the force must act on it. We call this resistance
INERTIA.
Important Vocab
 Inertia ______________________________________________________________________________
• sort of laziness
(inerzia – laziness in Italian)

Mass _____________________________________________________________________________
• more mass – harder to change velocity
____________________________________________________________________________
• depends only on the number and kind of atoms in it.
• doesn’t change due to gravity (same on moon as Earth)
Unit of Mass

Weight ___________________________________________________________________________________
• depends on its mass and acceleration due to gravity:
W = mg
The acceleration due to gravity on Jupiter is more than two times
greater than that on Earth. How would the following quantities
change on Jupiter?
Show 1 = Larger on Jupiter, 2 = smaller on Jupiter, 3 = no change
Your weight
Your mass
Your inertia
Forces
• ___________________________________________________________________________
• Causes objects to accelerate
NOTE: ALL forces are _________________________________ between 2 objects
Forces are vector quantities, having both direction and magnitude.
Unit of force
1 N is the force that causes a 1-kg object to accelerate 1 m/s2.
The net force – resultant force
is the ________________________________________________________________________________________
It is the net force that changes an objects motion!
Check your understanding
Newton’s 1st Law
BIG IDEA 1: Zero NET force means no acceleration / no change in velocity. Balanced forces will not cause
acceleration.
BIG IDEA 2: An object is in equilibrium (i.e. it has zero net force) whenever it has constant velocity (including
constant velocity of 0).
How is Newton’s 1st Law related to Galileo’s idea of inertia?
Problems
o An object at rest has two forces acting on it. One force is 8N to the left.
What is the other force?
o
An object that experiences two forces moves to the right with a constant velocity of 3 m/s. One force is 1N
to the right. What is the other force?
o
Six force are acting on an object. What can you tell about the motion of that object? Is it at rest? Is it
moving? If it is moving, how?
Newton’s Second Law
The acceleration of an object produced by a net force on
that object is directly proportional to the net force applied,
and inversely proportional to the mass of the object.
Direction of the acceleration is in the direction of the net
force.
How does mass affect acceleration?
… greater mass
_________________________________________________
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How does force affect acceleration?
… greater force
_________________________________________________
… zero force
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