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Newton’s Laws of Motion
(chapter 4)
Newton’s 1st Law of Motion
• An object at rest will remain there unless a force acts on
it; likewise, a moving object will continue forever unless a
force slows it.
• Or…unbalanced forces cause motion
Inertia and Mass
• Inertia is the tendency of an object to resistant a change
in motion
• The more mass…
• …the more inertia!
Law of Inertia and the 1st Law
Newton’s 2nd Law of Motion
• Force = mass x acceleration
• Acc = Force/mass
• Mass = Force/acc
• Force and mass are directly related
• Force and acc are directly related
• Mass and acc are indirectly related
• And finally, the label for force is the Newton.
• Newtons = (kg)(m/s2)
Gravity
• Definition – an attractive force between any 2 objects
• One of the 4 basic forces
• Law of Universal Gravitation
• Allows you to calculate the actual force between 2 objects
Earth’s gravitational acceleration
• Force = mass x gravitational acceleration
• F = m g (this is also known as the weight of the object)
• g = 9.8 m/s2
• http://www.factmonster.com/ipka/A0875450.html
Projectile motion
Centripetal force
• A force directed toward the center of curved path
• Centripetal acceleration is directed toward the center of a
curved path
Newton’s 3rd Law of Motion
• “for every action, there’s an equal and opposite reaction”
Momentum = mass x velocity = kg m/s
• Law of Conservation of Momentum
• Momentum never changes!