End of Year – Science Study
Guide
Forces and Motion
Forces and Motion
• Force – a push or a pull on an object
• Mass – the amount of matter that makes up
an object
• Matter – anything that has mass and takes up
space
Balanced/Unbalanced
Balanced Forces – forces acting on an object are equal in size
and opposite in direction (cancel each other out)
Examples :
• Holding a book in midair (balanced because book doesn’t
fall and you’re not lifting it)
• Pushing against a wall (the wall doesn’t push you over and
you don’t push it over)
Unbalanced Forces – forces that are not equal
Example:
• During a tug of war competition, one team pulls the other
team over the line (one team pulled with more force)
Inertia – Newton’s Law of Motion
An object at rest
An object in motion
Stays at rest
Stays in motion
Until another
force is applied
A heavier object is: more difficult to get in motion
and more difficult to slow down
A force must be applied to: make an object speed
up or slow down
An increase in speed leads to: an increase in
momentum
Gravity
• A force that pulls objects toward each other
(i.e. gravity pulls you toward Earth)
• The heavier an object…. The greater its pull of
gravity (the faster it will fall)
• If mass increases…. The force of gravity will be
greater on the object
• If distance increases… the force of gravity
acting on two objects is less than if they were
closer together.
Friction
• A force that acts between surfaces that touch each
other.
• The smoother the surface… the less friction there will
be between the objects (moves much quicker/harder
to slow down)
• Examples of a smooth surface: ice, tile floor
• The rougher the surface… the more friction there will
be between the objects (moves slower/easier to slow
down)
• Examples of a rough surface: road, carpet
Magnetism
• The force of pushing or pulling between
magnetic poles.
• Like poles… a repulsive force exists and
magnets move away from each other
• Opposite poles… an attractive force exists and
the magnets move toward each other
• The closer the objects… the greater the
magnetic force will be (strongest at the poles
of magnets)
Vocabulary
• Air Resistance – friction between a moving
object and air particles; acts against the pull of
gravity to slow a moving object (parachute)
• Position – the location of an object
• Motion - a change in an object’s position
Speed
Speed = distance/time
Speed of a ball thrown in the air:
• Rising – ball slows down as it rises higher and
higher until it stops
• Falling – ball goes from stopped position and
speeds up more and more as it falls to the
ground
Momentum
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Constant Speed
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Slowing Down
Losing Momentum
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Speeding Up
Gaining Momentum
• Increase in Momentum = increase in speed