Transcript force - cloudfront.net


Test Review

Test 3 = Questions 1,2,11,12,13,14,15,16
› 8 Total
› 12.5 points a piece

Test 4 = All the other question
› 17 Total
› 5.8 points a piece

“Find Someone Who” can tell you what
speed, velocity, and acceleration are.
› You must locate three different peers to tell you
what they think these terms mean and record the
answers in the “What we think” row of the
document.
› You are expected to answer as well as ask.
› It’s OK to be wrong but your must have and
answer
› The student who answers needs to sign his/her
name next to their answer.

2 minute time limit per word

Now list an “A” for agree or a “D” for
disagree next to the definitions

Turn to your shoulder partner and explain
why they agree or disagree with the
definitions.
› You have 2 ½ minutes
› GO

Update your handouts by recording the
scientific definitions of speed, velocity,
and acceleration in the “What We
Know” row of their handouts.

The PowerPoint will instruct you to record
examples as they complete their notes
on the handout.

The distance an object travels in a certain
amount of time.
› Average speed – Total distance divided by total
time
› Constant speed - Speed that does not change

On your paper, describe an example of an
object at a constant speed.
Speed equals distance divided by time.

On the side of your paper, calculate this
problem. Make sure you show all work!
A football field is about 100
meters long. If it takes a person
20 seconds to run its length,
how fast was the football
player running?
A football field is about 100 meters long. If it
takes a person 20 seconds to run its length,
how fast was the football player running?
› Speed = Distance ÷ Time
› Speed = 100 m ÷ 20 s
› Speed = 5m/s
Remember
to label the
UNITS!!

An object’s speed and direction at a
given time
› The wind is blowing 65 km/hr from the North.

On your paper, describe an example of
velocity.
A change in the direction or speed (velocity) of
an object over time – which may be:
› A change in speed
 Starting
 Stopping
 Speeding up (positive acceleration)
 Slowing down (negative acceleration)
› A change in direction
 Acceleration is caused by unbalanced forces.
 On your paper, describe an example of an
object accelerating.


How does your “What We Think” section
compare to your “What We Know”
section?

Does anyone notice any differences in
the meaning of the three terms? Explain.
› Speed is distance/time, velocity is speed
with a direction, and acceleration is a
change in speed and/or direction.

The terms we have noted are extremely
important in our upcoming unit of study.
Be prepared to refer back to them often.

Highlight, circle, or underline the key
points

http://www.youtube.com/watch?v=DRb
5PSxJerM

Title the next blank page Calculating
and Graphing Speed
You are going to draw 5 easy graph and
interpret the speed
The graph
shows an
object which is
not moving (at
rest).
The distance
stays the same
as time goes by
because it is
The graph shows
that the objects
distance increases
as time passes.
The object is moving
and so it has
velocity.
The straight line
shows it is a constant
(not changing).
Just like the
previous graph, this
graph shows an
object moving with
constant velocity.
The curve, in
the graph,
shows that the
object’s
velocity is
changing as
time passes.
This is
acceleration.
In the first part of the
graph, the object is
moving with constant
velocity.
In the second part of
the graph, the object
is at rest (not
moving).
In the third part, the
object is again
moving with constant
velocity.
LAB instructions
 Everyone is always recording
 Group Roles (you will rotate jobs)

›
›
›
›
›
Roller
Timer 1
Timer 2
Timer 3
Director
 Says Start and Stop
 Is in Charge


Continue the lab
Group Roles (you will rotate jobs)
›
›
›
›
›

Roller
Timer 1
Timer 2
Timer 3
Director
When you are finished sit back at your desk
and complete the graph and the questions
› Work together
› Turn in when you are finished
› Use COLOR on the graph





Directions:
1. Read the following scenario.
2. Calculate the average speed.
3. Briefly describe all points of acceleration and
explain.
A female cheetah left her cubs to hunt for food. She
sprinted 30 m away from her den in two seconds.
Next, she turned around and traveled 10 meters back
toward her den in three seconds. She suddenly
stopped and listened intently for two seconds. Then,
she traveled 40 meters away from her den in four
seconds.

With your face partner, sort the cards
into 3 groups

With your groups, write a 10 sentence story
using 2 of the four graphs.

Your story must include:
›
›
›
›
›
›
›
›
The average speed
Acceleration
Main Character
Plot
Be creative
10 pictures
Use two iPad
Be prepared to share

Write Tug of War on your warm up

Open Tug of War Handout in eBackpack

Open Change the Motion of an Object in
ebackpack
› You will answer the questions ON THE FIRST
PAGE as you complete the lab

Using the object that I give you make it
accelerate AT YOUR DESK!!!!!!!!!!!

Make it stop, start, speed up, slow down,
and change direction

Volunteer to Share

Pass out the laminated paper

With your should partner look at the
handout.

Describe the motion of the object.
› Such as: left, right, up, down

Then explain to your partner why your think
the object will move in a certain direction.
› Use words like: balanced, unbalanced, force,
motion and acceleration

Volunteer to share

Now you are going to start filling out the
rest of the paper from ebackpack

Copy what is in yellow and include a
quick picture

A change in the position of an object

Caused by force (a push or pull)
A push or pull on an object
 Measured in units called newtons (N)
 Measured with a spring scale
 Forces act in pairs

Types of Force: (pick two)
›
›
›
›
›
gravity
electric
magnetic
friction
centripetal

When all the forces acting on an object are
equal (net force is zero)

Balanced forces do not cause a change in
motion.

Balanced forces can change the physical
properties of an object without changing its
motion.

In your notes, describe an example of a
balanced force.

Cause the shape of an object to change
without changing its motion

Cause an object at rest to stay at rest or an
object in motion to stay in motion (inertia)

Cause an object moving at a constant speed
to continue at a constant speed

In your notes, describe an example of a
balanced force affecting an object.
1.
An object at rest will remain at rest until
acted upon by an unbalanced force.
2.
An object in motion will remain in motion
until acted upon by an unbalanced force.
3.
When all forces acting on an object are
equal (balanced)

When all the forces acting on an object are
not equal

The forces can be in the same direction or in
opposite directions.

Unbalanced forces cause a change in
motion.

In your notes, describe an example of an
unbalanced force.

Acceleration is caused by unbalanced
forces:
› slow down
› speed up
› stop
› start
› change direction
› change shape

In your notes, describe an example of an
unbalanced force affecting an object.

The total of all forces acting on an
object:
forces dodirection
not cause a are added.
› ForcesBalanced
in the same
change in motion.
 The object will move in the direction of the
force.
› Forces in opposite directions are subtracted.
 An object will move in the direction of the
greater force.

Open your notes from yesterday and
prepare to finish taking notes

Copy what is in YELLOW and include a
quick picture
10 N
30 N
http://commons.wikimedia.org/wiki/File:Jack-in-the-box.jpg
A child was playing with a jack in the box. The lid pushed
down with 10 N of force, while the spring pushed up with 30
N of force. What is the net force applied by the spring?
In your notes, calculate the net force and show all of your
work.
10 N
30 N
http://commons.wikimedia.org/wiki/File:Jack-in-the-box.jpg
A child was playing with a jack in the box. The lid
pushed down with 10 N of force, while the spring
pushed up with 30 N of force. What is the net force
applied by the spring?
30 N to the right + 10 N to the right = 40 N to the right
30 N
Tug of War
Game
50 N
Two competitors are playing tug of war.
What is the net force? Which direction will the rope
move?
In your note, calculate the net force and show all of your
work.
Tug of War
Game
30 N
50 N
Two competitors are playing tug of war.
What is the net force? Which direction will the rope
move?
50 N to the right – 30 N to the left = 20 N to the right

Open the Data Sheet in ebackpack

You are completing the first half of the
first page

You have 5 minutes to rotate around the
room and find three DIFFERENT partners.
You will combine arrows. You decide
which direction you want them to turn.
Fill in the chart

Mass is the amount of stuff (matter) in an object.
› The mass of an object will remain the same anywhere in the
universe.
› Mass is measured in grams or kilograms.

Weight is the mass (kg) of an object multiplied by the
acceleration of gravity (9.8 m/s2).
› The weight of an object depends on the gravitational pull of the
location in the universe.
› The gravitational pull on the Moon is only 1/6 of Earth’s gravitational
pull.
› Weight is measured in newtons (N).
Example: F=ma
A person with a mass of 25 kg x 9.8 m/s2 gravitational
acceleration is equal to 245 N of weight force.
F= 25 kg x 9.8 m/s2
F = 245 N
The person exerts 245 N of force on the ground.
If the person went to the Moon, they would only weigh
1/6
of 245 N.
Force (N) = mass (kg) x acceleration
(m/s2)
F
÷
m
x
a
Acceleration (m/s2) = force (N) ÷ mass
(kg)
F
÷
m
x
a
Mass (kg) = force (N) ÷ acceleration (m/s2)
F
÷
m
x
a
The acceleration of a sprinter is 10 m/s2. The force
exerted on the starting blocks is 650 N. What is the
mass of the sprinter?
Force =
Mass =
Acceleration =
The acceleration of a sprinter is 10 m/s2. The force exerted
on the starting blocks is 650 N. What is the mass of the
sprinter?
Force = 650 N
Mass = 65 kg
Acceleration = 10 m/s2
Mass = force ÷ acceleration
Mass = 650 ÷ 10
Mass = 65
A 56 kg cart is accelerating at 15 m/s2. Calculate the
force exerted on the cart?
Force =
Mass =
Acceleration =
A 56 kg cart is accelerating at 15 m/s2. Calculate the
force exerted on the cart?
Force = 840 N
Mass = 56 kg
Acceleration = 15 m/s2
Force (N) = mass (kg) x acceleration (m/s2)
Force = 56 x 15
Force = 840
A boat is pulling a 54 kg wake boarder. She
accelerates at 2 m/s2. Calculate the force that is
causing the acceleration.
Force =
Mass =
Acceleration =
A boat is pulling a 54 kg wake boarder. The force the
boat is exerting on her is 108 N. Calculate her
acceleration.
Force = 108 N
Mass = 54 kg
Acceleration = 2 m/s2
Acceleration = force ÷ mass
Acceleration = 108 ÷ 54
Acceleration = 2

Open the Data Sheet again

You are completing the second half of
the first page

You have 5 minutes to rotate around the
room and find three DIFFERENT groups of
three.
› Each group must have a Force, Mass, and
Acceleration card

The remaining two pages are homework
due tomorrow.

You may spend the rest of the period
working on them
A boat is pulling a 54 kg wake boarder. She
accelerates at 2 m/s2. Calculate the force that is
causing the acceleration.
Force =
Mass =
Acceleration =
F
÷
m
x
a

The total of all forces acting on an
object:
› Forces in the same direction are added.
 The object will move in the direction of the
force.
› Forces in opposite directions are subtracted.
 An object will move in the direction of the
greater force.
 Unbalanced
motion.
 Balanced
forces cause a change in
forces do not cause a
change in motion.

What is Force measured in?
› Newtons (N)

What is acceleration measured in?
› D/T
› Such as:
 m/s, miles/hour, ect

What is mass measured in?
› Weight
› Such as:
 Lbs, kg, ect

Remember Your Lab Safety Rules

You must show an understanding of
speed, velocity, and acceleration.

This is a Test Grade!

Call me over when you get to the
graphing part

Turn in your Effects of Unbalanced Forces
Experiment right now even if you are not
finished

Write test on your warm up log

Turn in your warm up log

Study your notes and labs for the next ten
minutes