Download Chapter 2: Forces

Chapter 2: Forces
2.1: Forces change motion
Vocabulary
• A push or a pull is called a
force
____________.
Vocabulary
contact force
• A ___________________
is when one
object pushes or pulls another
object by touching it. The first
object is applying this force to the
second object.
Vocabulary
Gravity
• _______________
is
the force of
attraction between
two masses.
• The strength of the
gravitational force
between two
objects depends on
their
masses
_______________.
Gravity pulls the
balls toward the
ground.
Vocabulary
Friction
• _______________
is a force that
resists motion between two
surfaces that are pressed
together.
Types of Forces
Gravity:
Pulls the skater toward the
ground.
Friction
Which surface would produce more
friction? How would that affect the motion?
Thinking Question
• Is force is a vector?
YES – it has both size
and direction!
Blue boxes
show mass
Vocabulary
• The overall force acting on an
object when all the forces are
combined is called the
net force
_____________________.
Balanced Forces
zero
1. If the net force on an object is _______________,
the
forces acting on it are balanced.
no
2. Balanced forces have the same effect as ________
forces at all.
Unbalanced Forces
Only an unbalanced
force can change the
motion
____________
of an
object.
Thinking Question
• Does an object always move when a
force acts on it?
No – if the forces are
balanced it will not
move.
Quick Review of Balanced and
Unbalanced Forces
Balanced
• __________________
forces cannot change
an object’s speed or
direction.
unbalanced
• An __________________
force is needed to
change an object’s
motion.
Forces on Moving Objects…
• To increase the speed of your bike, you may
more
exert ___________
forward force by pedaling
harder or changing gears. The net force
moves the bike faster.
unbalanced
• To turn your bike, you apply an ____________
force by leaning to one side and turning the
handlebars.
• To stop the bike, you use the extra force of
____________
that your brake pedals provide.
friction
Vocabulary
• An object at rest stays at rest, and
an object in motion stays in motion
unless acted upon by another
force is known as
Newton’s first law
_______________________________.
Unbalanced
force
Unbalanced force
(from the foot)
Object at rest
(ball)
Unbalanced
force (from
the hand)
Object in
motion (ball)
What unbalanced forces change the
motion of a volleyball that is hit hard over
the net? How will its velocity change?
The contact force of a hand
changes the ball’s direction,
and may increase its velocity.
Vocabulary
• The resistance of an object to a
change in the speed or the
direction of its motion is known as
inertia
_____________.
The passenger will
continue to move forward
and will hit the back of the
front seat.
Watch the video on Newton’s
First Law