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“Work and Simple Machines”

Lever Pulley Wheel and Axle

Wedge Screw Inclined Plane

4/19/12 Bell work …. ISN (p. 206)

®  Copy the question and answer in a complete sentence.

®  1)There are “simple machines” all around our school building. Make a list of as many examples of simple machines that you see in our school.

®  2)How can your arm be used as a simple machine? ®  ____________________________ ®  Paste the notes guide “Simple Machines” onto page

207 of your ISN. ®  Also paste the “ Uses for Simple Machines” practice

sheet onto page 209 in your ISN.

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What is work? ®  In science, work is done

when a force causes an object to move in the direction of the force.

®  Even the person in this picture is doing work by “applying force” to make the ball go the distance.

®  Work = force x distance ®  (W= f x d)

TCAP practice problem :

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TCAP practice question….

Answer: “D”

There is a difference between Force and Work……. ® Applying a force doesn’t always result in

work being done. ®  (Suppose you help push a stalled car. You push and push but

the car doesn’t budge. The “pushing” made you tired, but you haven’t done any work on the car, because the car hasn’t moved.You do “work” on the car, when the car actually moves.) Whenever you apply a force to an object and the object moves in the direction of the force, you have done work on the object.

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So when is work done on an object? ®  Work is done on an object

if two things happen: ®  A) the object moves as a

force is applied ®  b) the direction of the

object’s motion is the same as the direction of the force.

®  Is this lady in the picture holding the suitcases doing work?

Machines make work easier… ®  A machine is a device that

makes work easier by changing the size or direction of the force.

®  Machines are not just cars, big construction equipment, or computers.

®  You use simple machines everyday such as scissors, chopsticks, etc.

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The 6 Simple Machines

Lever Pulley Wheel and Axle

Wedge Screw Inclined Plane

Inclined Plane ®  The Egyptians used simple machines to build the

pyramids. One method was to build a very long incline out of dirt that rose upward to the top of the pyramid very gently. The blocks of stone were placed on large logs and pushed slowly up the long, gentle inclined plane to the top of the pyramid.

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Inclined Planes ®  An inclined plane is a

flat surface that is higher on one end

®  Inclined planes make the work of moving things easier.

®  Ex: ramps (on buildings and stairways, bath tubs)

®  Brainpop #1: Inclined planes

Wedges ® A wedge is a pair

of two incline planes that move.

® Wedges are used to split things.

® Examples includes an ax, a zipper, or cutting knives, plows, and chisels..

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Screws: are also incline planes

A screw is an incline plane that is wrapped in a spiral around a cylinder. When a screw is turned a small force is applied over the long distance along the incline plane of the screw. Meanwhile, the screw applies a large force through the short distance it is pushed. Screw are used mostly as fasteners.

Levers: ® A lever is a simple machine that has a

bar that “pivots” at a fixed point called a fulcrum. Levers are used to apply force to a load. (--A load is “what you are applying the force on”.)

Fulcrumà

ßeffort force (work input)

Resistance Force (load)à

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Example of Levers

.

®  Common examples of levers include crowbars, scissors, pliers, tin snips and seesaws.

More Levers …

® Other examples of levers include nut crackers, wheel barrows, doors, and bottle openers.

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Your arm acts as a lever

® Other examples also include tweezers, arm hammers, and shovels.

® Brainpop#2: "Levers"

Pulleys ® Pulley are simple

machines that have a grooved wheel.

® A pulley needs a rope, chain or belt around the groove to make it do work.

® A load is attached to the end of the rope and the input force is applied.

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Pulleys are all around your house…… ® When you open a

window blind by pulling on a cord, you are using a pulley.

Wheel and axle ® A wheel and axle is

a simple machine consisting of two circular objects of different sizes.

®  Did you know that faucets are examples of a wheel and axle?

®  Other examples include: (doorknobs, wrenches, steering wheels)

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WHEEL AND AXEL ®  Fan blades are

also examples of a wheel and axle. The axel is stuck rigidly to a large wheel. Fan blades are attached to the wheel. When the axle turns, the fan blades spin.

GEARS are Wheel and Axle ® Brainpop#4:

"Wheeel and Axle" ® Each gear in a

series reverses the direction of rotation of the previous gear. The smaller gear will always turn faster than the larger gear.

® 

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TCAP practice problem:

TCAP Practice problem:

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TCAP practice question….

Answer: “D”