Download Newton`s 1st Law Newton`s 2nd Law net Newton`s 3rd Law SI Units

Today’s Topics
• Newton’s Three Laws
• Mass and Weight
• Free Body Diagrams
Newton’s 2nd Law
A _______ is that which causes (unrestrained) objects to __________
Links forces to motion
We frequently can have knowledge of forces acting on an object
Can use the 2nd Law to translate the force into acceleration
Can then find velocity and position
Newton’s 1st Law
NET Force: ________________
If no NET _______ is applied to an object…
the object either remains at _______, OR
moves at a _________________
“At rest” is a special case of constant v, with v = 0!
Since _______ remains constant unless a net force is applied, objects
appear to be “_______”
Latin word for laziness: ___________
1st Law sometimes referred to as:
Force: Scalar or vector?
Mass: Scalar or vector?
Fnet=ma
Rolling cart – constant velocity?
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SI Units of Acceleration, Mass & Force
Newton’s 3rd Law
If one object exerts a force on a second object, the
________ object exerts a force on the _______
object
Quantity
Basis
g (at earth’s surface)
This “_________” force has a magnitude equal
to the first force
Mass
This “_________” force acts in the
_________direction as the first force
SI System
USC System
Mass-based
Force-based
9.81 m/s2
32.2 ft/s2
kg
slug
Force
N
pound
F=ma
1N = 1kg(1m/s2)
1lb = 1slug(1ft/s2)
SI System: kg linked to meter through H2O
Density of water is 1000 kg/m3 = 1 kg/L = 1 g/cm3
How are you able to stand on the floor?
How are you able to jump up off the floor?
USC System: two other force units
1 ton = 2000 lb
1 kip (kilopound) = 1000 lb
A couple of weeks ago we dropped a 10 ton wrecking
ball onto a Mini Cooper. Which object experienced
the greater force during that collision?
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Conversion Factors / Weight
Types of Forces
Force
Field Forces (act at a distance)
1 Newton = 0.2247 lb (~1/4 lb)
1 lb = 4.448 Newtons (~4.5 N)
What is a 200 lb professor’s weight in Newtons? _______
_____________________
_____________________
Mass
Contact Forces
1 slug = 14.594 kilograms
What is a 30 kg dog’s mass in slugs? _______
Ropes, cables, string
assumed to be flexible and of negligible mass;
Weight: force of gravity
tension the same everywhere
W = ______
Mass of an object is same everywhere - weight depends on location
200 lb on earth has a mass of ________
30 kg on earth has a weight of ________
force in the direction of the rope
Normal force: ___________
Friction force: ______________
Lazydog weighs 64 lb on the earth and gmoon is 5.31 ft/s2
Spring force: ____________
what is the dog’s mass on the moon? __________ slugs __________ kg
what is the dog’s weight on the moon? ___________ lb ___________ N
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Fnet=ma
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FBD = KD
____________________
Diagram of ______ free from
surroundings and showing all
________ that act on the body
Identify ___________
Draw ___________
Define a ______________
Draw all ________ that act ___ the body
Do not show ________________
=
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The Original Alabama Bass Tracker
_____________________
Diagram of ______ free from
surroundings and showing
___________________ (inertial) vectors
Alabama fan weighs 195 lbs. His “boat” and motor
weigh 218 lbs and the motor provides a force of
143 lbs. The drag resistance of the water is 62 lbs.
What is the acceleration of the boat?
What are the forces on the fisherman?
Draw same body
Show all __________ components
=
Runner starting a race:
Ball being thrown:
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