Gravity and Newton’s
Laws of Motion
What is a Force?
A push or a pull on an object in a
particular direction.
GRAVITY
An attractive force that exists between all
objects that have mass.
This force is dependent on mass and
distance from the object.
GRAVITY
The closer the objects are, the stronger the
gravitational force
The more massive the objects are, the stronger
the gravitational force
Check out
this
simulation
UNIVERSAL GRAVITATION
The law of universal gravitation states that the force of
gravity acts between all objects in the universe.
video
MASS vs WEIGHT
video
MASS vs WEIGHT
Mass:
Amount of matter in an object.
Measured in grams or kilograms
What is the difference?
Weight: Is the gravitational force exerted on an
object.
Your weight is actually a force measured in Newton’s.
Your weight on other planets
HAMMER FEATHER MOON DROP
Video on the Moon
Video in a vacuum
chamber
GETTING TO MARS
Newton’s Laws of Motion
First Law – Objects at rest stays at rest and an object in motion
keeps moving with the same speed unless an outside force acts
on it.
• The space shuttle just sits on the launch pad without moving
until a force is acted on it.
Examples
• Tablecloth trick
• Car accidents
Tablecloth Trick
Myth video
Mythbusters
video
GETTING TO MARS (CONTINUED)
• Newton’s Second Law - The amount of force needed to make an
object change its motion depends on the mass of the object.
• Larger force – larger acceleration
• Larger mass – smaller acceleration
F=MA
Example: It is easier to push an empty shopping cart than a full
one, because the full shopping cart has more mass than the
empty one.
GETTING TO MARS (CONTINUED)
• Third Law – When one object exerts a force on a second object,
the second object exerts an equal and opposite force back on
the first
• “For every action there is an equal and opposite reaction”
• The space shuttle is pushing exhaust down, so the exhaust must
be pushing the space shuttle up
SHUTTLE NEWTON’S THREE LAWS
video
HYPOTHESIS
You are a NASA engineer trying to get the first person to Mars. You
need to get the space shuttle to a speed of 100 m/s within 1 km.
You and your team have been having trouble making it travel
faster and disagree on how to fix it.
Half of the team says to add more force
Half of the team says to decrease the mass of the space shuttle.
Who do you think is correct? Explain your answer.
INVESTIGATION
Half of the team says to add more force
Half of the team says to decrease the mass of the space shuttle.
Task: Conduct an experiment to either support or oppose each
method given the following materials.
• String
• Matchbox car
• Tape
• Washers
• Paper clips
• Stopwatch
Take 3 minutes discuss the task, and how you plan to conduct the
investigation, collect data, and interpret results.
Add more force to the shuttle
Remove some extra mass
from the shuttle
As the mass of the shuttle decreases, what happens to
the acceleration of the shuttle?
increases
As the amount of force applied to the shuttle increases,
what happens to the acceleration of the shuttle?
increases
WHO WAS RIGHT?
Both were correct. Either removing mass from
the shuttle or adding more force would
increase the acceleration of the shuttle.