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ForceA push or pull that has a size and a direction.
Makes objects speed up, slow down, or change direction.
OR
Inertia Measures an object’s tendency to
resist changing its motion.
Inertia depends on the amount of mass an object has.
More Mass = More Inertia
Less Mass = Less Inertia
Unless acted upon by a force, objects in motion tend to stay in motion and objects at rest
remain at rest.
Balanced ForcesForces that cancel each other out because they
are equal and acting in opposite directions.
The scale doesn’t move because it is balanced. Because
balanced forces cancel each other
out, there is
NO MOVEMENT!
Unbalanced ForcesUnequal forces that do not cancel
each other out.
The scale moves because it is unbalanced.
Because unbalanced forces do not cancel
each other out,
there IS
MOVEMENT!
Friction
Force that resists motion between two touching surfaces.
Friction between your shoes and the skateboard keeps you from
sliding off as you slow down.
If there were no friction, you would not be able to walk! Your shoes would not grip the ground
and you would slide.
Without friction you would not even be able to pick anything up, because you would not be
able to grip the object. It would slip out of your hands!
To get the most out of friction, we even wear special shoes like baseball cleats, soccer cleats,
basketball shoes and track shoes.
Friction wears objects down. This is why the bottoms of your
shoes slowly disappear and why your parents have to buy new
tires for the car.