FORCE AND MOTION UNIT
7TH GRADE SCIENCE
2007
GLOSSARY OF TERMS
POSITION
The location of an object. X is
the abbreviation/variable for
position.
GLOSSARY OF TERMS
MOTION
A change in an object’s position
relative to a particular reference
point.
GLOSSARY OF TERMS
ACCELERATION
The rate of change of velocity or
how quickly an object’s velocity
changes.
Units: m/s2
GLOSSARY OF TERMS
FORCE
A measure of the amount of push
or pull acting on an object.
Units: Newtons (N). 1N=force
needed to accel. 1kg at 1m/s2
GLOSSARY OF TERMS
FRICTION
A force that OPPOSES the
motion of two objects in contact.
TYPES: sliding, rolling, wind
resistance, drag.
GLOSSARY OF TERMS
INERTIA = “laziness”
Resistance to changes in motion
in any object with mass.
More Mass = More Inertia
FIRST LAW OF MOTION
Objects in motion will remain in
motion in a straight line and at a
constant speed; objects at rest will
remain at rest; unless the object is
acted on by an unbalanced force.
FIRST LAW OF MOTION
THE BIG IDEA:
FORCES are the ONLY things that can overcome
inertia and cause changes in motion.
FIRST LAW OF MOTION
EXAMPLES: pebble in space
Person in a car crash – without a seatbelt?
2ND LAW OF MOTION
The acceleration (change in
motion) of an object is
determined by the size of the
force and the mass of the object.
THE BIG IDEA...
Bigger masses need bigger forces to
accelerate them.
Bigger accelerations take bigger forces.
2ND LAW OF MOTION
FORMULA: F = m x a
TRIANGLE:
3rd LAW OF MOTION
When one object pushes a second object
with a force there is always an opposite
force from the second object pushing on
the first.
BIG IDEA...
Each action force has an equal and opposite
reaction force. Forces are always “TWINS”