Download Newton`s Laws of Motion

Newton’s Laws of Motion
I. Newton’s 1st Law of Motion - Inertia
 Law states that an object at rest will stay at rest, or an
object in motion will stay in motion unless a force
acts upon it
o What does it mean by a force?
 A push or pull in a specific direction
 examples: gravity, magnetism, air, friction
 contact force - force touches object
 non-contact force - force does not touch
object
o What is a balanced force?
 a force that is equal in strength and opposite in
direction
 they cancel each other out so the force = 0
Newtons
 results in no motion
o What is an unbalanced force?
 a force that is unequal and moves towards the
stronger force
 if the forces (arrows) are going in the same
direction  add the forces together
 if the forces are going in different directions 
subtract the forces
o We use a vector (or an arrow) to show the direction
and strength of a force
 the longer the arrow, the stronger the force
 the shorter the arrow, the weaker the force
 Other things to know about Inertia
o What is a mass?
 the amount of “stuff” or matter in an object
 more mass = more inertia
 less mass = less inertia
II. Newton’s 2nd Law of Motion
 F = ma (force = mass x acceleration)
o units for each
 force - Newton (N)
 mass - kilograms (kg) or grams (g)
 acceleration - meters per second squared (m/s2)
o Using the F=ma formula
 Solving for Force
 F = ma mass times acceleration
 answer is in Newtons (N)
 Solving for mass
 m = F / a force divided by acceleration
 answer is in kilograms (kg)
 Solving for acceleration
 a = F / m force divided by mass
 answer is in meters per second squared
(m/s2)
 Other things to know about Newton’s 2nd Law
o Mass vs. weight
 mass always stays the same
 weight changes with gravity
 weight is the force of gravity on an object
 more mass = more gravity
 more distance = less gravity
o acceleration
 acceleration to Earth due to gravity is always 9.8
m/s2
III. Newton’s 3rd Law of Motion
 Law states that for every action, there is an equal and
opposite reaction
o examples: walking, kicking your foot back to make the
skateboard to move forward, swimming, a bird
flapping its wings to make it fly, the space shuttle
taking off