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• First, rank the following words from 0-5 (0= you have never heard of this word & 5= you know the word VERY well). Second, explain what the following terms mean in your own words:– Machine
– Simple machines
– Work
– Force
– Work input/Work output
– Lever
-Pulley-Wheel & axle-Inclined plane-Wedge-Screws-Compound machine
BELLWORK 4/6/15
Simple Machines
April 6, 2015
• Differentiate between the six simple machines. (SPI 0707.11.1)
• Determine the amount of force needed to do work using different simple machines. (SPI 0707.11.2)
TEXTBOOK:
• A machine is a device that makes work easier by changing the size or direction of a force.
• Examples: wheelchair, scissors, chopsticks
TEXTBOOK:
• A machine or simple device without moving parts.
• Examples: lever, pulley, wheel & axle, inclined plane, wedge, screw
TEXTBOOK:
• Work is the transfer of energy to an object by using a force that causes the object to move in the direction of the force.
• Work is done on an object if two things happen: 1) the object moves as a force is applied, 2) the direction of the object’s motion is the same as the direction of the force.
• Examples: pushing a ball up a hill
OR ORYES NO YES NO
To be considered work the direction of what two things must
the same?
Force and Motion
Work or Not Work?• Problem #1:
–D.J. carries a backpack from the cafeteria to the 8th grade hallway.
• Problem #2:
–Austin applies force to (pushes) a brick wall.
Work or Not Work?• Problem #3:
–Mya pushes a stack of books across the floor.
• Problem #4:
–Alexis wears a backpack and climbs up the side of a mountain.
TEXTBOOK:• A push or a pull
exerted on an object in order to change the motion of the object; force has size and direction.
• Examples: people, bulldozer, static electricity
The equation for WORK is…
work= force x distance
or
W = F x D
Work Problem #1:--Kammi uses a lever to lift a large stone
from the ground. Kammi applies a force of 50 newtons and moves the stone 5 meters. How much work is being done by Kammi?
Work Problem #2:--Mariah wants to move a stack of
magazines from one room of her house to another. Using a wheel and axle, Mariah applies a force of 100 newtons and moves the stack 10 meters. How much work is being done by Mariah?
The equation for FORCE is…
Force = work_________
distance
or
F = W / D
Force problem #1:--Tabetha performed 100 joules of work
by moving a pile of rocks 10 meters with a lever. What was the force on the rocks?
Force Problem #2:-Cameron performed 500 joules of work
by lifting a car 50 meters with a pulley. What was the force on the car?
TEXTBOOK:
• Work input is the work done on the machine.
• Work out put is the work done by the machine.
• Examples: opening a paint can
The Six Simple Machines
The Six Simple MachinesLever
TEXTBOOK:
• A lever is a simple machine that has a bar that pivots at a fixed point, called a fulcrum.
• Examples: first-class lever (see saw), second-class lever (wheelbarrow or soda bottle opener), third-class lever (lifting weights or hammering a nail)
Write the question & answer.
First-Class Lever Second-Class Lever Third-Class Lever
Elementary School Middle School High School
First-Class Lever Second-Class Lever Third-Class Lever
2nd class- the load is between the fulcrum and the force
3rd class- the force is between the load and the fulcrum
Elementary School Middle School High School
1st class- fulcrum is placed between the load and the force
Which of the following correctly explains why one of the above levers can lift the object with less effort force? A.Lever X will require less effort force because its fulcrum is closer to the object than lever Y's fulcrum.B.Lever Y is a third-class lever and will require less effort force than lever X, which is a second-class lever.C.Lever X is a third-class lever and will require less effort force than lever Y, which is a second-class lever.D.Lever Y will require less effort force because its fulcrum is closer to the input force than lever X's fulcrum.
The Six Simple MachinesLever Pulley
TEXTBOOK:
• A simple machine that has a grooved wheel that holds a rope or a cable.
• Examples: fixed, moveable, block and tackle
The pulley changes the direction of the force. Elevators make use of fixed pulleys.
Movable pulleys do increase force, but they also increase the distance over which the input force must be exerted.
A fixed pulley and a movable pulley are used together; the mechanical advantage of a block and tackle depends on the number of rope segments.
Which of the pulley systems shown below will lift the weight using the least amount of effort force?
The Six Simple MachinesLever Pulley Wheel & Axel
TEXTBOOK:
• A simple machine consisting of two circular objects of different sizes.
• Examples: car’s wheel & axle, faucet
Effort force applied to a wheel is ____________ when it is transferred to the axle because the axle travels a
___________ distance than the wheel.
A.multiplied, longer B.divided, longer C.multiplied, shorter D.divided, shorter
The Six Simple MachinesLever Pulley Wheel & Axel
Inclined Plane
TEXTBOOK:
• A simple machine that is a straight, slanted surface; a ramp.
• Examples: ramp or slide
The Six Simple MachinesLever Pulley Wheel & Axel
Inclined Plane Wedge
TEXTBOOK:
• A simple machine that is made up of two inclined planes that move; often used for cutting.
• Examples: knife, axe, door stop
Select the choice that best completes the following sentence. When an axe is used to chop wood,
A.the axe blade acts as a wedge and changes the direction of the input force.B.the axe blade acts as a wedge and does not change the direction of the input force.C.the axe blade acts as a lever and does not change the direction of the input force.D.the axe blade acts as a lever and changes the direction of the input force.
The Six Simple MachinesLever Pulley Wheel & Axel
Inclined Plane Wedge Screw
TEXTBOOK:
• A simple machine that consists of an inclined plane wrapped around a cylinder.
• Examples: screw, light bulb
Which of the screws below requires the least amount of effort force to turn?
W. X. Z.Y.
TEXTBOOK:
• A machine made up of more than one simple machine.
• Examples: manual can opener
TEXTBOOK:
• A machine’s mechanical advantage is the number of times the machine multiplies force; how much easier it is to do the work using that specific machine.
• Examples:
Mechanical AdvantageMechanical Advantage
It is 10 times easier to use a ramp to move a heavy object.
• Agendas and HW (p.271-273 in workbook) out on desk!!
• Answer your Bellwork in your composition book.
• What type of machine can be found on at least half the students in this room right now? What kinds of machines were common 50 years ago? 100 years ago? Are any of the same machines around today that were common in the 1800s? What has changed about those same machines today?
BELLWORK 3/14/12
• Agendas out on desk!!
• Answer your Bellwork in your composition book.
• Think about the differences between the six simple machines. Which simple machines could you use to raise heavy objects? Which simple machines could you find in a kitchen? Describe how you would use these machines.
BELLWORK 3/15/12