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Newton’s Laws
By Kevin Lui and Dennis Tao
Newton’s First Law
Law of inertia- in the absence of an unbalance applied force, the
body at rest remains at rest and a body already in motion
remains in motion with a constant velocity. This rule only applies
if the object is moving in a straight line.
Example of
Newton’s First
Law
Example Problem
If the sum of all the forces acting on a
moving object is zero, the object will:
 1. slow and stop
 2. change the direction of its motion
 3. accelerate uniformly
 4. continue moving with constant
velocity
Answer
Choice (4) because according to
Newton's first law, in there is no
outside force an object at rest will
remain in rest and an object in
motion will remain in motion.
Newton’s Second Law
The acceleration of an object is directly proportional to the
net external force acting on the object and inversely
proportional to the object’s mass.
Net Force = Mass x Acceleration
Example of Newton’s Second Law
Example Problem
What is the gravitational acceleration on a
planet where a 2 kilogram mass has a
weight of 16N on the planet's
surface?
 1. 1/8 m/s^2
 2. 8 m/s^2
 3. 10 m/s^2
 4. 32 m/s^2
Answer
Choice (2), because according to
Newton's 2nd law, acceleration is
equal to Force divided by mass.
Acceleration = Net Force/Mass
Acceleration = 16N/2 kg
Acceleration = 8 m/s^2
Newton’s Third Law
For every action there is an equal and
opposite reaction.
Example of
Newton’s Third Law
Example Problem
A man is pushing a baby stroller. Compared
to the magnitude, or amount, of force
exerted on the stroller by the man, the
magnitude of the force exerted on by the
stroller is
 1. zero
 2. smaller but greater than 0
 3. larger
 4. the same
Answer
Choice (4) because according to
Newton's 3rd law, any action has an
equal and opposite reaction. So, the
magnitude of force the stroller exerts
back and the magnitude of force
exerted by the man are the same
Homework
Holiday Packet Q7,36
AMSCO pg 28 Q 98
Demo
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First Law: http://www.youtube.com/watch?v=uOSBC0SXVR4
Second Law:
http://www.youtube.com/watch?v=UhCG0qoY9Dc&playnext=1&li
st=PLE7CB081021BD828F&index=5
Third Law: http://www.youtube.com/watch?v=mNM5tHou4IQ