1. NEWTON’S 3rd LAW

2. Newton’s 3rd Law and Gravity
-Newton’s 1st law stated:
An object at rest tends to ____________________________
an object in motion tends to __________________________
as long as the forces are balanced.
stay at rest
stay in motion
-Newton’s 2nd law states (part 1):
When an unbalanced force acts on an object, the object will
___________________ in the direction that the unbalanced force
points.
-Newton’s 2nd law states (part 2):
Force = __________ x ___________________
accelerate
acceleration
mass

3. equal force (This is called recoil or kickback)
-Newton’s 3rd law states:
-whenever an object exerts a force on a second object, the
second object exerts an ___________________ back on the
first object.
equal force
-Commonly stated as: For every action there is an equal and opposite reaction.
(This is called recoil
or kickback)

4. Push hot gases The 3rd Law says out the back of the gases must push
-Rocket Motion
-On Earth we use air and Bernoulli’s principle to allow flight.
Since there is no air in space, how can a vehicle be propelled?
Push hot gases
out the back of
the rocket
The 3rd Law says
the gases must push
equally back on you
and your rocket.

5. object falling forever.
-Gravity
-Gravitational force (or gravity) is the force of ____________ that
exists between any two pieces of _____________.
-Gravity on Earth is always in affect, pulling all objects towards the
center of the Earth.
attraction
matter .
-An orbit is just an
object falling forever.

6. masses distance big small very big very small
-The attraction of objects with the Earth is just one example of gravity at
work. According to Newton, any two objects that are composed of
matter attract each other, but there are rules for the strength of this
attraction.
-Universal Law of Gravitation states:
-the amount of gravitational force between two objects depends
on two things:
1) the ___________ of the objects and
2) the ___________ between the objects
masses
distance
-Big masses = _______ g. force -Big distance = ________ g. force
-Big masses & short distance = _____________ g. force
-Small masses & large distance = _____________ g. force
big
small
very big
very small

7. Weight = ____________ x _____________________
-Weight and mass are NOT the same.
-Mass is constant and measures the amount of _____________.
-Weight is just a measure of the _______________ on an object.
-since the larger mass = larger attraction, the more mass an
object has the more weight it has.
matter
gravitational force
Weight = ____________ x _____________________
W = ___ x ___
- On Earth, gravity accelerates all objects at _________.
Ex. How much does an 80 kg man weigh on earth?
gravitational acceleration
mass
(N)
(kg)
(N/kg) m g
~10 m/s2
m = 80kg g = 10 m/s2
W = m x g
W = 80kg x 10 m/s2
W = 800 kg x m/s2 = 800 N
-However, since weight depends on the gravitational force
between the two objects (ex. yourself and Earth) your weight will change if you leave Earth.
-Weight on the moon is about ______ of the weight on Earth.
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