Transcript AirNormalTension

Types of Forces
Let’s begin with some skydiving movies.
http://www.manifestmaster.com/video/
Gravity
Friction
①
Air Resistance
Definition
Air resistance is the FORCE that OPPOSES the
motion of another object through the air.
Your teacher (or a volunteer) is going to drop
two pieces of paper: one piece of paper is flat
and the other is crumpled up.
Which piece of paper is going to hit the ground first?
② Predict
③
Observe
④ Explain
⑤
Draw arrows and label the force of gravity (Fg)
and the force of air resistance (Far)
Far
Fg
⑥
Terminal Velocity
Terminal velocity is the CONSTANT
velocity (speed) that a falling object
reaches when GRAVITY and AIR
RESISTANCE are balanced.
⑦
The two forces acting on a skydiver jumping out of an
airplane are GRAVITY and AIR RESISTANCE.
⑧ Draw arrows and label the force of gravity (Fg)
and the force of air resistance (Far).
Far
ANIMATION
http://www.waowen.screaming.net/revision/for
ce&motion/skydiver.htm
Fg
How would skydiving be different on the
Moon?
Fg
⑨
The Moon has no ATMOSPHERE (no air).
Therefore there is NO air resistance on the Moon.
⑩
Empty space (a place with no air)
is called a VACUUM.
⑪
What will happen if a flat piece of paper and crumpled piece of paper
are dropped at the same time on the Moon? Will one piece land first?
⑫
FREE FALL is the name given to
objects falling that experience
the force of gravity but no air
resistance.
Simulation of Galileo’s free fall experiment...ignoring air resistance.
http://www.visionlearning.com/library/flash_viewer.php?oid=1884
⑬
NORMAL FORCE
Normal force is a force (usually a push) that
is PERPENDICULAR to the surface of contact.
The symbol for NORMAL FORCE is FN
⑭
Perpendicular means
AT RIGHT ANGLES
or
AT 90
DEGREES.
DEFINITION: http://www.merriamwebster.com/dictionary/normal
⑮ Push against a wall. Draw an arrow
and label the normal force
FN
The force a table exerts on a book.
FN
⑯
Comparing normal force to friction:
Friction force is PARALLEL to the contact surface.
Normal force is PERPENDICULAR to the
contact surface.
⑰
Tension Force
The pull of a ROPE or STRING is called a TENSION force.
The symbol for the force of tension is
FT
⑱
Spring (Elastic) Force
The pull or push of a SPRING, RUBBER BAND, or
BOUNCY BALL is called SPRING FORCE.
The symbol for the spring force is
Fs
Now let’s try
Identifying Interactions
in
Realistic Situations