Chapter 5, Sections 2, 3, 4 Matter in Motion
Essential Ideas / Vocabulary
Name __________KEY___________
Explanation
A push or a pull
Measured in Newtons (N)
Examples / Drawings
With a force, an object in motion
could speed up, slow down, or change
direction
Force
Net Force
Results from combining all the forces
exerted on an object
Forces in same direction – add the
forces
Forces in opposite direction – subtract
smaller force from larger force
You and your friend are playing tug of
war. You exert a force of 25N and
your friend exerts force of 30N. What
is the net force and who will win the
war?
30N – 25N = Net force of 5 N and your
friend wins
Are the forces balanced?
Explain.
Forces are balanced
(gravity pulling
down and cards
pushing upward)
and cards do not fall
Net force is 0 N and the object does
not move
Balanced Forces
down
Produces a change in motion that
results in an object moving
Unbalanced Forces
Friction
Diagram:
A force that opposes motion between
two surfaces that are touching.
Created when the “hills” and “valleys”
of surfaces (even when they appear to
be smooth) stick to one another.
Are the forces balanced? Explain.
Forces are
unbalanced and
the person may
fall (force
forward/force
downward)
*More “hills & valleys” = more friction
*Less “hills & valleys” = less friction
*Greater forces = more friction
*Amount of surface area touching =
same amount of friction
Friction is necessary
When is friction needed?
Tires on Road, brakes, shoes on floor,
rubber bottom on bath mat
Increase Friction
Ways to increase friction: rough up a
surface, add sand/gravel, increase
mass (greater force between surfaces)
Tile is slick when wet, so
getting out of shower you
step on rug to dry
your feet – friction
keeps you from
slipping / falling
vs
Race cars have slick tires to allow car
to go faster, but less traction so they
spin out more quickly… regular cars
have “rougher” tires to be able to grip
the road to increase friction and avoid
spinouts
Decrease Friction
Gravity
Law of Universal Gravitation
Ways to decrease friction: lubricants
(oils, grease, wax, water),
smooth/sand surface, ball bearings (in
skates/wheels)
Force of attraction between objects
due to their masses.
Two factors that affect gravity are
mass and distance.
All objects in the universe attract each
other through gravitational force. The
size of the force depends on the mass
of the objects and the distance
between them.
Define: amount of matter in an object
Mass (review)
Tool used to measure: balance scale
Increase gravitational force by
increasing mass and/or decreasing
distance between objects.
Decrease gravitational force by
decreasing mass and/or increasing
distance between objects.
How change?
Grow from baby
Diet
Pump iron (build muscle)
SI Unit: g
Define: amount of gravitational force
on an object due to its mass
Weight (review)
Tool used to measure: spring scale
SI Unit: N
How change?
Change mass
Change location/leave planet