Transcript Forces

On the white board…
In your own words,
how would you
explain or describe
FORCES?
Forces
Chapter 10
Today we will
Describe forces using task cards,
Cornell Notes, and a word map.
1. The nature of forces
2. Force – what is it?
3. Push or a pull
3. Has a magnitude and direction
3. SI unit is Newton (N)
4. Named after Sir Isaac Newton
2. Combining Forces
3. Net force – what is it?
4. Combination of all forces added
together
4. Determines which direction an
object moves
4. Determines if an object moves
4. Must take in the direction when
adding them.
3. Examples
What is the net force for the following
problems?
a. 10 N
4N
b. 3 N
6N
STOP
QUESTIONS –
PERSON B BEGINS
2. Unbalanced forces
3. Net force will cause an object to
change the object’s velocity.
3. Examples
4. People pushing a box
4. Swing
4.
4.
2. Balanced Forces
3. Forces acting on an object that do not
cause a change in the velocity of that
object.
3. Examples
4. Two people pushing a box with equal
force in opposite directions
4. Balancing a book on your head.
4.
STOP
QUESTIONS –
PERSON D BEGINS
In class strategy
Create a word map for the
word …
FORCE
Today we will…
Discuss Friction, Gravity,
and Elastic Forces using
Cornell Notes and Choice
Strategies.
1. Various forces and laws
2. Friction – what is it?
3. Force that two surfaces exert on
each other when they rub against
each other.
3. Strength of the force depends on
the type of surface and how hard
they push together
2. Types of friction
3. Static friction
4. Acts on objects that are not moving
3. Sliding friction
4. Two solid surfaces slide over each other
3. Rolling friction
4. When an object rolls across a surface
3. Fluid Friction
4. Solid object moves through fluid
2. Gravity
3. A force that pulls objects toward each
other
3. Acts everywhere, not just Earth
4. Universal Law of Gravitation
3. Force between the objects increases with
greater mass and decreases with greater
distance
3. Weight = mass x gravity
acceleration (9.8m/s2)
Mass = lbs / 2.2
Mass x 9.8 = your weight in N
2. Gravity and Motion
3. Free fall
4. The force of gravity alone causes an
object to accelerate in the downward
direction.
3. Air resistance
4. Fluid friction that acts on objects falling
through the air
3. Projectile
4. Any object that is thrown.
2. Elastic forces
3. Matter is considered elastic if it returns to
its original shape after it is squeezed or
stretched.
3. Compression
4. Elastic force that squeezes or pushes
matter together
3. Tension
4. An elastic force that stretches or pulls
matter
Homework
2 Choice Strategies
Today we will
Explain how Newton’s law of
motion play a role in forces
using Cornell Notes.
1. Newton’s 3 laws of
motion.
2. Newton’s 1st law of motion
3. An object will remain at rest or moving
at a constant velocity unless it is acted
upon by an unbalanced force
3. Also called the Law of Inertia
4. Inertia is the tendency of an object to
resist change in motion and depends
on mass
2. Newton’s 2nd law of motion
3. Acceleration
depends on the net
force action on the object and on
the object’s mass
3. Acceleration = Net force / Mass
2. Newton’s 3rd law of motion
3. If one object exerts a force on
another object, then the second
object exerts a force of equal
strength in the opposite direction
on the first object.
3. For every action, there is an equal
but opposite reaction
3. Action – reaction pairs
4. Jumping off the ground
5. Feet push off the ground = action
5. Ground pushes back with equal force =
reaction
4. Others???
http://video.foxnews.com/#/v/4580409/anat
omy-of-a-tsunami/?playlist_id=86861
http://video.foxnews.com/#/v/4581353/cata
strophe-in-japan-/?playlist_id=86857
http://www.cnn.com/2011/WORLD/asiapcf/0
3/12/japan.before.after/index.html?hpt=T1
http://www.cnn.com/video/#/video/world/20
11/03/13/nr.nye.nuclear.reactors.cnn?iref=
allsearch
2. Momentum
3. Momentum = mass x velocity
3. SI units are kg x m/s
3. Has a direction and magnitude
3. More momentum = harder to
change the velocity
2. Conservation of Momentum
3. Total momentum of any group of
objects remains the same, or is
conserved, unless outside forces
act on the objects.
3. Can be transferred from one object
to another
Practice problems
Page 392 #’s 1a, 2, 3, 4
Page 399 #’s 1 -5
Chapter 10 and 11 Review
White board review for Bonus Points
Forces can be added together
only if they are
A. Acting on the same object
B. Balanced forces
C. Unaffected by gravity
D. substantial
Which type of elastic force is
present on the strings in a guitar?
A. Compression
B. Tension
C. Friction
D. Inertia
True or false
Unbalanced forces do not change the
object’s motion.
True or False
Mass and air resistance affect the
gravitational attraction between two
objects.
True or False
The property of matter that resists a
change in motion is called inertia.
Snowshoes enable a person to
walk on deep snow because the
snowshoes.
A. Decrease the person’s weight on the snow
B. Increase the area over which the person’s
weight is distributed.
C. Increase the pressure on the snow.
D. Increase the buoyancy of the person.
A barometer is used to measure
pressure
A.
B.
C.
D.
In the atmosphere
Under water
In hydraulic systems
Under a snowshoe
Which of the following is true of
the buoyant force?
A.
B.
C.
D.
It acts in the downward direction
It acts with the force of gravity
It acts in the upward direction
It makes an object feel heavier
Flight occurs because of
A.
B.
C.
D.
Archimedes’ principle
Pascal’s principle
Bernoulli’s principle
Newton's third law of motion
True or False
When the only force acting on a
falling object is air resistance, the
object is said to be in free fall.
Pascal’s principle helps to
explain
Hydraulic brakes
Buoyancy
Momentum
Flight
In physical science, a push or a
pull is called a(n)
A. Force
B. Acceleration
C. Inertia
D. Motion
Completion
A(n) __________ is an object that is
thrown.
The total momentum of a group
of objects is conserved unless
A. Outside forces do not act on the
objects
B. Outside forces act on the objects
C. The objects are moving
D. There are more than two objects
True or False
Newton’s third law of motion states
that for every action there is an
equal but opposite unbalanced
force.
Which of the following examples
demonstrates a compression
force?
A. Plucking a guitar string
B. Pulling a wagon
C. Squeezing a sponge
D. Dropping an apple
Completion
What are the units for momentum?
True or false
Friction depends on the types of
surfaces involved and how hard the
surfaces push together.
Completion
What is the formula for momentum?
How can you increase the
momentum of an object?
A. By decreasing its velocity
B. By increasing its mass
C. By increasing its friction
D. By decreasing its acceleration
True or false
According to Newton’s second law of
motion, weight depends on an
objects mass and the net force
acting on the object.
Completion
The overall force on a object after all
the forces are added together is
called the ___________ force.
Completion
Unbalanced forces acting on an
object produce a change in the
object’s _________.
Completion
Wet pavement is more slippery than
dry pavement because the force
needed to overcome ___________
friction is less than the force
needed to overcome sliding friction.
Completion
The force of gravity between you and
Earth is greater than the force of
gravity between you and a car
because Earth has more ______
than the car.
Completion
The downward force acting on an
object in free fall is the force of
_____________.
Completion
The metric unit that is most often
used to describe weight is the
____________.
Completion
A person traveling in a car that stops
suddenly keeps moving forward due
to __________.
Completion
According to Newton’s third law of
motion, the strength of a reaction
force is _________ the strength of
the action force.
Completion
Friction acts in a direction
___________ to an objects direction
of motion.
What happens when two forces
act in the same direction?
A. They cancel each other out
B. The stronger one prevails
C. They add together
D. Their sum divided by two is the
total force
Completion
The momentum of an object is in the
same _________ as its velocity.
How does the momentum of a 4 kg
bowling ball rolling at 3 m/s
compare to the momentum of a 6
kg bowling ball rolling at 2 m/s?
A.
B.
C.
D.
The bowling balls have equal momentum.
The 4 kg bowling ball has more momentum
The 6 kg bowling ball has more momentum
There is not enough information to compare
the two bowling balls.
Completion
As the distance between two objects
decreases, the gravitational force
between them ________________.
White Board Review
On your white board, answer the
following questions.
The combination or addition of all the
forces is called a
_________________________.
A force that two surfaces exert on
each other when they rub against
each other is called ____________.
Pressure can be measure in units
of
A.
B.
C.
D.
Newtons
Newtons per square meter
Newtons per centimeter
Newtons per cubic centimeter
What are the four types of friction?
What is an object that is thrown
called?
This is the SI unit for force.
Mass x Velocity =
Equal forces acting on one object in
opposite directions are called
_____________.
What is the definition of force?
What is the definition for unbalanced
forces?
Give an example of static friction?
The pressure resulting from a force of 50N
exerted over an area of 5 square meters is
______________ Pa.
Pressure ____________ as the area over which
a force is distributed increase.
The unit of pressure is called the
____________.
Water pressure ___________ with depth.
A substance whose shape can
easily change is a
A.
B.
C.
D.
Solid
Powder
Fluid
Metal
A material that can easily flow is
called a
A.
B.
C.
D.
Fluid
Solid
Buoyant force
Hydraulic material
Air pressure decreases as
A.
B.
C.
D.
Velocity increases
Elevation increases
Acceleration decreases
Gravity increases
If an object floats, the volume of
displaced water is equal to the
volume of
A. The entire object
B. The portion of the object that is above
water
C. The portion of the object that is submerged
D. Exactly half of the object
When water fills a submarine’s
flotation tanks, the overall
density of the submarine
A.
B.
C.
D.
Decreases
Stays the same
Increases
Reduces the buoyant force
What is the formula for density?
One application of Pascal’s
principle is
A. A hydraulic car lift
B. The flight of an airplane
C. A speedboat’s bottom slapping against the
waves
D. The buoyancy shown by ducks and other
waterfowl.
What scientific rule describes
why water squirts from a plastic
bottle when it is squeezed?
A.
B.
C.
D.
Bernoulli’s principle
Archimedes’ principle
Pascal’s principle
Newton’s first law of motion