Force and Motion
Inertia
Tendency of a motionless object to
remain motionless
Force
A push or pull on an object
Backward push
When you apply a force on the ground
with your foot to move forward
Forces That Affect Motion
-Gravity (pulls things towards the Earth)
-Distance affects gravity (objects are
closer there is more gravity; farther apart
there is less pull between them
-Friction (an object’s resistance to move)
-When two surfaces touch you get
friction; friction causes an object to slow
down and eventually stop
-Friction occurs in the opposite direction
you are trying to move an object
-Mass (the amount of matter that makes
up an object)
-Determines how much force is needed
to change an object’s motion
-Less mass moves farther and faster
-More mass needs more force to move it
the same distance
Speed
A measure of how far an object moves
in a given period of time
Speed= distance/time
Velocity
A measure of speed with the direction of
the movement
Factors That Affect Speed
-Variables can affect speed
-Slope (the distance covered while
coming down from a height)
-Height can affect the speed of an
object on a ramp (speeds it up)
-Friction can affect the speed of an
object (slows it down)
-Weight DOES NOT affect the speed of
an object
-Weight (a measure of the pull of gravity
on an object)
*Gravity doesn’t care about mass so the
objects will accelerate at the same
speed (Our experiment outside on the
playground- EVERYTHING fell at the
same speed)
Work
Scientifically defined as being done
when a force MOVES an object
-Force gives energy to objects
-Resistance forces are gravity and
friction and to do work you have to
overcome these
Ex: Pushing on a wall IS NOT work;
Carrying a box up stairs IS work; carrying
a box down the hallway in your arms IS
NOT work
Unbalanced Force
When the total force on an object is
moving in one direction; changes the
motion of an object
Balanced Forces
Newton’s 1st Law
Newton’s 2nd Law
Forces that are exerted in opposite
directions but equal in size and strength
Law of Inertia (An object with no
unbalanced force acting on it will either
remain at rest or continue to move at a
constant speed until a force acts on it)
Law of Acceleration (F=ma)
When an unbalanced force is applied to
an object, the object accelerates
-It moves in the direction of the force
and the greater the force, the faster the
object moves
Newton’s 3rd Law
For every action or force, there is an
equal and opposite reaction/force