Marvelous, Simple Machinesfor 7th grade

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Activity Guide• Challenge: Discuss (10 minutes)• Generate Ideas and Multiple Perspectives (instructor choice)• Research and Revise (and Test Your Mettle)

– Activity 1: rotate through stations (25-30 minutes)• In groups of 4 or 5, students rotate to each of the six simple machine stations to

conduct tests.• Students record data in “Testing Simple Machines” worksheet

– Activity 2: Review (10 – 15 minutes)• Discuss/compare “Testing Simple Machines” worksheet as a class• Look at images of real-life simple machines and discuss each

– Activity 3: (25-30 minutes)• Complete “Testing Simple Machines” worksheet

– convert grams to Newton’s in chart– convert metric units in the “Challenge” to English units

• Go Public: (instructor choice)– Revisit the Challenge– Design a solution and communicate it in writing with sketches

Teacher tips• It helps to set up the simple machines and use them before class.• Set up each simple machines on a separate table.• Groups of 4-6 students will rotate to each table to use/test each simple

machine and record their data.• It is beneficial to discuss that a simple machine does not reduce work, it

typically makes it ergonomically easier. It the force needed to move an object is reduced, then the distance to move it typically increases (look at an inclined plane for an example –distance is how far the object moves on the plane, not the height it ascends)

• The larger simple machines – lever, pulley and inclined plane are stored in the equipment room on the right near the door.

• The lever, Hall’s cart, wheel and axle, cart without wheels, and pulley already have string attached. If this string is not present, you have an extra spool, along with a pair of scissors, in the storage cart for 7th grade. You may ignore the directions to attach the string if it is already attached.

Teacher Prep

• Assemble materials listed on next page• Set up stations– Each simple machine will be set up on a different table

resulting in 6 stations, 1 for each simple machine– Use the materials guide on the next page to set up your

stations– Each group of 3-5 students receives 1 copy of “Testing

Simple Machines” chart to complete.• Students will rotate to each of the simple machine

stations to make their observations – spending about 4-5 minutes at each station

Materials• Lever*

– Lever– 1 spring scale– 1 200 mg weight

• Incline Plane*– Incline plane– Hall’s cart– 1 spring scale

• Pulley*– Pulley stand with 2 pulleys attached– 1 extra pulley– 2 spring scales– 1 200 gram weight with hook

• Wheel and axle– 1 wooden car with wheels– 1 wooden car without wheels– 1 spring scale– 1 200 gram weight with hook

• Screw– 1 wooden block with bolt– 1 hex-head driver– 1 ruler with English units

• Wedge– 1 wedge– 1 block of wood with bungees attached– 1 rubber mallet

• 6 copies of “Testing Simple Machines” in mechanical room filing drawer on bottom left

• Pens/pencils

*These larger pieces are stored in the equipment room to the right as you walk in. They are bungeed in place, please return them to this location when you have completed the lab. Thank you!

Location of all MaterialsDrawer 3b1:• 28 mechanical pencils• 1 spool parachute cord• 1 pair scissors• 1 ruler• 2 metric measuring tapes• 5 200 gram aluminum weightsDrawer 3b3:• 6 spring scalesDrawer 3b4:• 1 blue Hall’s cart• 1 wooden wheel & axle• 1 wooden car without wheels• 1 wedge stand wrapped with bungees• 1 wooden wedge• 1 block with hex bolt inserted• 1 hex head driverIn equipment room on left• 1 incline plane• 1 lever• 1 pulley stand with pulleys and string

ChallengeYou are a mechanical engineering consultant. Your client has asked you to design a conveyor belt from simple machines that will move a 40 kg box directly from the loading dock door to a counter in another room.

• The box is 1 meter tall x 0.75 meters wide x 1.5 meters long• The box must be moved across a 5 meter x 9 meter room and up

on top of a counter that is 1 meter from the floor, 0.5 meters wide and 3 meters long.

3 M

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9 M long

10 3 M long wall

BoxCounter

5 M

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Guiding Question

• What is a simple machine?– Name the six simple machines– What do they do? How do they work?– Identify real-world examples of simple machines

• What is work?– Do simple machines reduce the total amount of

work required to do an activity?– Explain your answer.

Worksheet

Activity 1

• Activity 1: rotate through stations– In groups of 4 or 5, students rotate to each of the

six simple machine stations to conduct tests.– Students record data in “Testing Simple Machines”

worksheet(25-30 minutes)

Lever

Fulcrum

Hang 200 gram mass on end of lever.

Hang spring scale on opposite end of lever.

• Pull spring scale until lever is level.

• Record the “effort” that the spring scale indicates in units of grams in your Testing Simple Machines Chart.

Now move mass to hole nearest lever stand. Pull the spring scale to level the lever. Record

“effort” from spring scale.• Note that we decreased the

distance of the mass from the fulcrum (point where the lever attaches to the support).

• How will this affect the force needed to raise the weight of the mass?

• What could you do to make it harder (use more force) to raise the weight?

Remove the mass and scale from lever.

• Return the materials to the places that you found them.

Incline Plane

Set up cart

• Set 200 gram mass on the Hall’s cart.

Raise the incline plane to the 9th hole from the bottom. Secure with pin.

Place Hall’s cart at bottom of incline plane. Pull the string up and over pulley.

Make sure incline plane is at the edge of the table and the string dangles from the pulley off the edge of the table.

Attach a spring scale to the loop in end of the string hanging off the table.

Pull the spring scale down toward the floor to pull the cart up the plane. Record the “effort” in grams registered on the spring scale in your Testing Simple Machines chart.

• Pull the cart up the incline by pulling down on the scale attached to the string.

• Record the “effort” that the spring scale registers while you are pulling on the cart. Record in grams in the “Testing Simple Machines Chart.”

Raise the incline plane to the 18th hole from the bottom. Secure with pin.

• Note that we are doubling the angle of the incline plane.

• How will this affect the “effort” force needed to pull the Hall’s cart up?

Place Hall’s cart at bottom of incline plane with string pulled up plane and over pulley.

Make sure incline plane is at the edge of the table and the string dangles from the pulley off the edge of the table.

Attach a spring scale to the end of the string hanging off the table.

• Pull the spring scale down toward the floor to pull the cart up the plane.

• Record the “effort” registered on the spring scale in grams in your Testing Simple Machines Chart.

Remove weight from cart.

• Return the materials to their original location on the table.

Pulley

Hang a 200 gram mass from one of the loops on the single pulley. (The pulley with the

string pulled through it.)

Be sure to hold onto the other side of the string when you are hanging the weight.

Hang a spring scale from the other loop.

Pull the spring scale down until you see how much “effort” force is needed to lift the mass.

Record the “effort” from the spring scale in units of grams that is needed to lift the weight of the mass in your “Testing Simple Machines Data Chart.”

Return the materials to their original location on the table. You are ready for the double pulley.

Set up the double pulley system.

• Use the right side of the pulley stand.

• Allowing the pulley to hang down from to the left, pull the loose end of the string up and through the pulley from the right to the left.

Thread end of string up to the top pulley (the one where the string is secured).

• Making sure to hold onto the looped, free end of the string, hang a 200 gram mass from the pulley.

• Pull the looped end of the string down and hang a spring scale that measures units of gram from it.

Pull down on the spring scale and take a reading from the spring scale

Tip: make sure the pulley does NOT get stuck on the bolt in the pulley stand.

• Read the “effort” that is needed to lift the 200 gram mass.

• Record this in your Testing Simple Machines Chart.

Remove spring scale, mass, and pulley.

Return the materials to their original location on the table. You are ready to move on to the next station.

Wheel and Axle

Set the 200 gram mass on the car without wheels

Pull the car without the wheels across your table with the spring scale.

• Record the “effort” measured in grams from the spring scale that is required to move the cart in your “Simple Machines Data Chart.”

Place the 200 gram mass on the car with wheels.

Use the spring scale to pull the car with wheels across your table.

• Record the “effort” force required to pull the car in your “Simple Machines Data Chart.”

• How does this force compare to the force required in the car without wheels?

Remove weight and spring scale.

• Return materials to their original place on the table.

Screw

Put the bolt in the block of wood. Screw it in so that it is 1-inch from the top of the block.

Put the hex-head driver on the bolt.• Line up the line on the block with the line on

the top of the hex-head driver.

Use the ratchet to screw in the bolt.• Count how many turns it takes to screw the

bolt in 1-inch. Record in your “Simple Machines Data Chart.”

• How could this make work easier. Name a practical example.

Return materials to their original location on the table.

Wedge

Use the handles to try to pull apart the blocks of wood.

Record the effort that you expended to pull the blocks of wood apart in your Testing Simple Machines chart.

Put the wedge at the indented slot between the two blocks of wood.

Use the rubber mallet to hammer the wedge between the two blocks of wood.

• How much force did you use?

• How did this compare to trying to pull the wood apart?

• Record your findings in your “Simple machines Data Chart.”

Tip: KEEP fingers AWAY from the space between the blocks of wood!!!! It will PINCH.

Carefully remove wedge from block of wood by tilting the wedge to the side and pulling it up and out.

Return materials to original location.

Activity 2

• Discuss/compare “Testing Simple Machines” worksheet as a class

• Look at images of real-life simple machines and discuss each

(10-15 minutes)

Which type of simple machine is this?

• How does it work?

What type of simple machine is this?• How does it work?

What type of simple machine is this?

• How does it work?

What type of simple machine is this.

How does it work.

What type of simple machine is this?

• How does it work?

What type of simple machine is this?How does it work?

Activity 3: Calculations (25-30 minutes)

• Complete “Testing Simple Machines” worksheet– convert grams (g) to Newtons (N) in chart

• We measured mass units from the spring scale and now we need to calculate the force applied, the “effort,” by using Newton’s 2nd Law, Force = Mass x Acceleration

• These measurements were taken in an earth setting where the acceleration acting on a mass in the vertical direction is due to earth’s gravity, taken at sea level to be 9.81 m/s2

• Convert the metric units in the “Challenge” to English units, meters => feet– Always good to know unit conversions, and what a great way to

reinforce math with ratios!• 2.54 cm = 1 inch 100 cm = 1 m 12 inches = 1 foot

Go Public – Revisit ChallengeYou are a mechanical engineering consultant. Your client has asked you to design a conveyor belt from simple machines that will move a 40 kg box directly from the loading dock door to a counter in another room.

• The box is 1 meter tall x 0.75 meters wide x 1.5 meters long• The box must be moved across a 5 meter x 9 meter room and up

on top of a counter that is 1 meter from the floor, 0.5 meters wide and 3 meters long.

3 M

wid

e w

all

9 M long

10 3 M long wall

BoxCounter

5 M

wid

e

Vocabulary• Simple machine - requires application of only one force to work• Force – the amount of effort necessary to do work; usually measured

in pounds (lbf) or Newtons (N)• Lever

– The fulcrum is the pivot point about which the lever rotates or turns.• Pulley• Inclined plane• Wheel and axle• Screw• Wedge• Work = force x distance; the amount of force needed to move an

object a given distance

Simple MachinesSimple Machine How does it work? Real world

example(s)Lever A lever is a stiff rod that rotates around a pivot point. Downward

motion at one end results in upward motion at the other end. Depending on where the pivot point is located, a lever can multiply either the force applied or the distance over which the force is applied.

Teeter totter, scissors, crowbar, toilet flusher, clippers, stapler, bottle opener…

Inclined Plane An inclined plane is a slanting surface connecting a lower level to a higher level. The longer the inclined plane, the less force required, but greater distance required to move a load. Shorter planes = more force, but less distance.

Roller coaster, dump truck, stairs, parking ramp, wheel chair ramp …

Pulley A pulley is a rope wrapped around a grooved wheel. A single pulley simply reverses the direction of a force. When two or more pulleys are connected together, they permit a heavy load to be lifted with less force. The trade-off is that the length of the rope must move a greater distance than the load.

Rock climber pulleys, clothesline pulley, flag pole pulley, drapery or shade pulleys…

Wheel and Axle In this machine a wheel or spoke is locked to a central axle so that when one is turned the other must turn. A longer motion at the edge of the wheel is converted to a shorter more powerful motion at the axle. In reverse, a short powerful force at the axle will move the wheel's edge a greater distance.

Door knob, bicycle, roller skates, windmill, fan …

Screw A screw is a central core with a thread or groove wrapped around it to form a helix. While turning, a screw converts a rotary motion into a forward or backward motion (linear motion).

Jar or bottle lid, cork screw, piano stool, drills, screws …

Wedge A wedge is two inclined planes back to back forced into a solid object. A wedge converts motion in one direction into a splitting motion that acts at right angles to the blade.

Chisels, sledge hammer, car tire wedge,