MARCH 26, 2014
Homework: Read pgs. 48-50, define highlighted terms
from reading and pick two main ideas from each
heading- leave spaces for additional notes (on pg. 7 in
N.B)…
Do Now: Write down homework: Open notebooks to pg.
5 and open textbooks to pg. 46.
UNIVERSAL GRAVITATION
-Acts everywhere in the universe, not
just on Earth.
- Law of Universal Gravitation: the force
of gravity acts between all objects in
the universe.
Any two objects in the universe, without exception, attract
each other.
You are attracted to the Earth and the Earth is attracted to you
FACTORS AFFECTING GRAVITY:
• Mass and distance are the two factors that affect
gravitational attraction between two objects.
• Mass is the measure of the amount of matter in an object.
• SI unit : kilograms (kg)
• Mass and gravitational force: the more mass an object has,
the greater its gravitational force.
• If mass increases, the force of gravity increases
• Ex: the sun’s mass is so great it exerts a large gravitational
force on the planets.
DISTANCE BETWEEN OBJECTS:
• The farther apart two
objects are the less
gravitational force
there is between them.
• If the distance
between two objects
increases, the force of
gravity decreases
WEIGHT AND MASS
• Weight is the measure of gravitational force on an object
-the force of gravity on a person or object at the
surface of a planet
• It varies with the strength of gravitational force, mass
does not.
• Gravity pulls on mass. Your mass in kilograms (kg)
multiplied by the force of gravity (9.8 m/s²) = your weight.
(1 kg= 2.2 lbs)
-What forces are
acting on a sky
diver, as they fall
from the sky?
-Write a question you
have about the forces
that act on a falling
object?
---Could there be
anymore than what
you have written?
-What happens to the
force of gravity between
two objects when the
distance decreases?
-What is the difference
between mass and
weight?
-Why do you weigh less on
the moon than you do on
Earth?
MARCH 27, 2014
Homework: Section Assessment
Questions: 2C, 3A, and 3B- on
pg. 10 in your notebook
Do Now: Write down
homework, Update T.O.C- pg8:
Gravity and Motion
Pg. 9: Air Resistance activity
Open notebook to page 7-
~~~GRAVITY AND MOTION~~~
• Gravity, the downward force that affects all objects, and
air resistance, fluid friction, both affect motion.
**When you hold something then let go…
• Gravity becomes the unbalanced
force that causes the object to fall
• Is the ball falling faster when it
leaves your hand or when it is just
about to hit the ground?
GRAVITY CAUSES ACCELERATION
• Acceleration means speeding up, slowing down, or
changing direction.
Gravity Causes:
--objects to accelerate;
--an objects velocity (speed) to increase, when it has been
dropped from any height
--an object to change direction, when it is thrown
horizontally
PROJECTILE MOTION
Projectile: An object that is thrown
Gravity acts the same on objects moving
horizontally as it does for objects moving
vertically.
-Gravity eventually pulls horizontally moving
objects downward, at the same rate as
objects dropping vertically
WHICH HITS FIRST?- ACTIVITY
• Besides gravity, what force acts on falling objects?
• Air resistance
• Why did it take the flat piece of notebook paper longer
to reach the ground?
• Because it has a larger surface area, so the force of air
resistance is greater.
AIR RESISTANCE• Air resistance is a type of fluid friction- that acts on a solid
object moving through the air and in opposite direction of
motion.It is an upward force exerted on falling objects
• Not the same for all objects
• Falling objects with a greater surface area
will have more air resistance.
ex: a leaf falls more slowly than an acorn
WHAT IF THERE WAS NOT ANY
AIR RESISTANCE?
• Because all objects freefall at
the same rate 9.8 m/s²- no
matter what their masses are.
• When dropped, two objects
with different masses would hit
the ground at the same time.
FREE FALL
• An object is in free fall when
the only force acting on it is
gravity.
• When in free fall the object
is accelerating---Why?
• Because the force of
gravity is an unbalanced
force, which causes the
object to accelerate
-All objects accelerate,
because of gravity at a rate
of 9.8 m/s---no matter what
their masses are.
TERMINAL VELOCITY
• The greatest velocity a falling object
reaches- when the force of air
resistance equals the weight of the
object.
• Air resistance increases with Velocity
• A falling object will eventually fall
fast enough that the upward forceair resistance and downward force
–gravity become equal.
(**REMEMBER**)When forces are
balanced no acceleration
the velocity (speed) remains
constant (even).
PROJECTILE MOTION
Projectile: An object that is thrown
Gravity acts the same on objects moving
horizontally as it does for objects moving
vertically.
-Gravity eventually pulls horizontally moving
objects downward, at the same rate as
objects dropping vertically
-What forces are
acting on a sky
diver, as they fall
from the sky?
What does the
skydiver experience
during his fall to the
Earth?
MARCH 28, 2014
• Homework: Read pgs. 51-53: Review notes: and begin
Force packet- pages 1-4 due for check in on Tuesday
• Do Now: Write down homework, put force packet away,
Open notebooks to page. 10
• Today I will… create a diagram that demonstrates why
objects accelerate during free fall…
• Identify Newton’s 3 Laws of motion
MARCH 28, 2014
• Homework: Read pgs. 51-53: Review notes: and begin
Force packet- pages 1-4 due for check in on Tuesday
• Do Now: Write down homework, put force packet
away, Open notebooks to page. 7/ 8
• Today I will… create a diagram that demonstrates
why objects accelerate during free fall
• Identify Newton’s 3 Laws of motion
AIR RESISTANCE• Air resistance is a type of fluid friction- that acts on a solid
object moving through the air and in opposite direction of
motion.It is an upward force exerted on falling objects
• Not the same for all objects
• Falling objects with a greater surface area
will have more air resistance.
ex: a leaf falls more slowly than an acorn
WHAT IF THERE WAS NOT ANY
AIR RESISTANCE?
• When dropped, two objects with
different masses would hit the
ground at the same time.
• Because all objects freefall at the
same rate 9.8 m/s²- no matter
what their masses are.
FREE FALL
• An object is in free fall when
the only force acting on it is
gravity.
• When in free fall the object
is accelerating---Why?
• Because the force of
gravity is an unbalanced
force, which causes the
object to accelerate
-All objects accelerate,
because of gravity at a rate
of 9.8 m/s---no matter what
their masses are.
TERMINAL VELOCITY
• The greatest velocity a falling object
reaches- when the force of air
resistance equals the weight of the
object.
• Air resistance increases with Velocity
• A falling object will eventually fall
fast enough that the upward forceair resistance and downward force
–gravity become equal.
(**REMEMBER**)When forces are
balanced no acceleration
the velocity (speed) remains
constant (even).
• 2C: How would your weight change on the surface of an EarthSized Planet whose mass was greater than Earth’s? Why?
• Your weight would be greater because the gravitational
force is greater
• 3A.Why does an object accelerate when it falls toward the Earth’s
surface?
• Gravitational force causes the object to accelerate toward the Earth
• 3B: How does the mass of an object affect its acceleration during
free fall?
• An objects mass has no effect on its acceleration during free fall.
• http://www.youtube.com/watch?v=LEs9J2IQIZY--Force and Gravity &
Friction
• http://www.youtube.com/watch?v=yHFtk6Si0Fk- school house rock
-What forces are
acting on a sky
diver, as they fall
from the sky?
What does the
skydiver experience
during his fall to the
Earth?
NEWTON’S BIG 3
Newton’s Three Law’s of Motion:
1st: Law of Inertia, objects at rest will stay
at rest, objects in motion will stay in
motion
2nd: The force needed to move an object
is equal to the product of that objects
mass and Acceleration; F= m x a
3rd: For every action there is an equal and
opposite reaction.
NEWTON’S 1ST LAW
• 1st: (Law of Inertia) Objects that are at rest, stay at rest. Objects that
are in motion will stay in motion at constant velocity (speed) unless an
unbalanced force acts on it, which accelerates the object.
• Inertia: the tendency to keep moving. It depends on the mass of the
object. The more mass an object has the more inertia..
NEWTON’S 2ND LAW
• 2nd: The force needed to move an object is equal to the product of
that objects mass and Acceleration; F= m x a
NEWTON’S 3RD LAW
• 3rd: For every action there is an equal and opposite reactions
Projectile motion
How does gravity affect objects that are moving horizontally?
Highlights!
• Is the ball falling faster when it
leaves your hand or when it is just
about to hit the ground?
It falls faster when
it hits the ground
-When you throw a baseball, how can you tell that
the force of gravity is acting on it?
• The ball eventually falls to the ground
What happens to the force of gravity between two objects when the distance decreases?
What is the difference between mass and weight?
-Why do you weigh less on the moon than you do on Earth?
1) Is the object moving?
2)What type of friction is this an example of?
3) What is the Net force of these forces?
4) What would you have to do to break this force of friction?
1) Label all the forces acting on the sky diver as she
toward the Earth’s surface-Draw the arrows to show strength and directi
the forces and what forces those arrows represent
2) Write if the forces are balanced or unbalanced and
unbalanced in what direction is the net force actin
*Note:*Assume that picture B. is when terminal veloci
occurred.
3) For picture C. What force changes when a sky diver
parachute opens? What forces stay the same?
NEGATIVE DIRECTION OF THE NET FORCE
• http://www.bbc.co.uk/schools/scienceclips/ages/8_9/friction_fs.shtml
• Force can be in the negative direction when pointing to the left or
downwards.
FIG. 3 IN BOOK>