Activity 5.3.3 Simple Machines Explo-rations

IntroductionNow that you know all about simple machines, let’s try building some of these amazing devices to see exactly how they make work easier. We first started using machines to make work easier and faster. How much easier and faster a machine makes your work is the mechanical advantage of that machine. The mechanical advantage (MA) is the number of times a machine multiplies your effort force.

In this activity you will design and perform experiments to demonstrate how different machines make work easier. You will make samples of simple machines and calculate the mechanical ad-vantage of a simple machine that you test.

Equipment• GTT notebook• Pencil• Calculator• Pulleys• Nylon string• Spring scale• Wooden frame/dowel rod for hanging fixed pulleys• Ruler, tape measure, yard stick, or meter stick• Weights• Brick• Cardboard (to make calculations easy, the cardboard should be cut to 10 in. long and at

least 4 in. wide)• 2 in. x 4 in. x 6 in. – 2 boards for wedge activity• 2 wood chisels with different angles and width• 2 door stops• Screwdrivers• Hammer• Awl• Wood screws, machine screws, drywall screws• 2 in. x 4 in. x 6 in. – 2 boards for screw activity• VEX pieces to build a seesaw• Nutcracker• Hard candy-like jaw breakers (for cracking with nutcracker)• Masking tape

ProcedureAs you travel to the six stations, follow the directions to complete the simple machine building and exploration activities. Don’t forget to include units on all measurements.

Your teacher will tell you when to move to the next station. If you complete the activity at that sta-tion and have extra time, answer the conclusion questions for the appropriate simple machine at the end of this activity.

STATION 1: PULLEYPulleys are very flexible because they use ropes to transfer force rather than a rigid object such as a board or a rod. Ropes can be routed through virtually any path. They are able to abruptly change directions in three dimensions without consequence. Ropes can be wrapped around a motor's shaft and either wound up or let out as the motor turns.

A) One Pulley

Use the 1 pulley set up. How much weight are you moving? _____g (HINT- the amount of weight is the same in each of the three pulley arrangements.)

• How many Newtons of force does it take to move the weight? _____N• Measure the length of rope needed to lift the weight from the table to the top pulley. Mea-

sure from the spring scale to the top pulley. _________inches

B) Two Pulleys

Use the two pulley set up. The new pulley is called a moveable pulley because it will move up and down as you pull on the string. Pull down on the spring scale.

• How much weight are your moving? ________g (HINT- the amount of weight is the same in each of the three pulley ar-rangements.)

•• How many Newtons of force does it take to

move the weight? ________N• Measure the rope from the spring scale to

the top pulley. How many inches of rope are needed to lift the weight from the table to the top pulley? ________inches

• How is this different from using only one pul-ley?

• The MA of a pulley is equal to the number of supporting ropes. What is the MA of this pul-ley system?

C) Four Pulleys

Use the four pulley set up. Pull down on the spring scale.

• How much weight are you moving? _____g• How many Newtons of force does it take to

move the weight? _________N• What is the MA of this pulley set up?

_______• Measure the rope from the spring scale to

the top pulley. How many inches of rope are needed to lift the weight from the table to the top pulley? ________inches

• How is this different from using only one pul-ley?

• The MA of a pulley is equal to the number of supporting ropes. What is the MA of this pul-ley system?

Question:What do you predict the spring scale will measure if you have six pulleys to move the 500 g? Explain your answer.

I think the scale would measure ______N because ___________________________________________

___________________________________________

STATION 2: INCLINED PLANETo build your inclined plane, you will use the same brick and piece of cardboard. Just turn the brick on each` of its three sides as represented in the diagrams. Use the same weight attached to a spring scale to slide up the inclined plane in each example. To find the MA of an inclined plane, divide the length of the piece of cardboard by the height of your brick.

1. Place the brick and cardboard on the table as shown. Record the following measurements (don’t forget your units).

• Length of sloped surface __________inches• Highest point of inclined plane ______inches• Figure MA = length/height: _________• How much weight are you moving? _____grams• How many Newtons of force does it take to move the

weight? ________N

2. Place the brick and cardboard on the table as shown. Record the following measurements (don’t forget your units).

• Length of sloped surface __________inches• Highest point of inclined plane ______inches• Figure MA = length/height: _________• How much weight are you moving? _____grams• How many Newtons of force does it take to move the

weight? ________N

3. Place the brick and cardboard on the table as shown. Record the following measurements (don’t forget your units).

1. Place the brick and cardboard on the table as shown. Record the following measurements (don’t forget your units).

• Length of sloped surface __________inches• Highest point of inclined plane ______inches• Figure MA = length/height: _________• How much weight are you moving? _____grams• How many Newtons of force does it take to move the

weight? ________N• Which inclined plane required the least amount of ef-

fort to move the weight?

• Why?

• Which inclined plane had the highest MA?

• Why?

STATION 3: SCREWWith the use of a screwdriver, each person in the group will screw each of the three different types of screws into a board. You may make a pilot hole with a hammer and awl if necessary to get the screw started. Before starting, look at the three screws and discuss with your group which one you think will go into the board the easiest. What is your prediction?

1. Hold a ruler parallel to the threaded shaft, count the number of threads in one inch, and record the value as:

• Threads Per Inch (TPI) _________________________

• Record the diameter of where the effort is ap-plied ______in__ (screwdriver handle)

• Calculate the circumference of the screwdriver handle: Circumference = лd or 3.14 * diameter = ____________in___

The pitch of a screw is the vertical distance between two adjacent screw threads. One complete revolution of the screw will move it into an object a distance equal to the pitch of the screw. The pitch of any screw can be calculated using the formula Pitch = 1/TPI.

• The pitch of this screw is ________mm__

• The MA = circumference/pitch. What is the MA of this screw? ____________________________________

Wood Screw

Pitch = Distance be-tween Threads

1. Hold a ruler parallel to the threaded shaft, count the number of threads in one inch, and record the value as:

• Threads Per Inch (TPI) _______________________

• Use the same screwdriver and record the cir-cumference you calculated in the previous ques-tion. ________in.___

Drywall Screw

• Calculate the pitch of this screw. _____________mm_____

• Calculate the MA of this screw. ___________________

1. Hold a ruler parallel to the threaded shaft, count the number of threads in one inch, and record the value as:

• Threads Per Inch (TPI) _______________________

• Use the same screwdriver and record the cir-cumference you calculated in the previous ques-tion. ________in.___

• Calculate the pitch of this screw. _____________mm_____

• Calculate the MA of this screw. ___________________

• Which screw went into the wood fastest? Why?

• Which screw turned easiest? Why?

Machine Screw

STATION 4: WEDGEThe wedge is a modification of the inclined plane. Use the two different chisels to carefully carve on the wood blocks. Record the following measurements of your two chisels (don’t forget your units). The MA of a wedge can be found by dividing the length of either slope by the thickness of the big end.

1. Chisel #1:

• Length of sloped surface ______mm• Widest point of the wedge ______mm• Calculate the MA = Slope/Thickness

_____________________________

W1. Chisel #2:

• Length of sloped surface ________mm• Widest point of the wedge _______mm• Calculate the MA = Slope/Thickness

_____________________________

1. Which chisel was easiest for you to use and why?

2. Two door wedges are located at your station. Calculate the MA for each wedge and explain which one you think will hold a heavy door open. Test your prediction with a door in your class-room.

STATION 5: LEVERThere are three different classes of levers. The class of lever is determined by the location of the fulcrum in relation to the resistance force and the applied force.

1. A first class lever has the fulcrum between the ef-fort and resistance. Use the ruler and block provided to build a seesaw.

• Measure the distance from the fulcrum to the re-sistance. ________in.___

• Measure the distance from the fulcrum to the ef-fort. ________in.___

• MA = effort arm length / resistance arm length. Calculate the MA of the lever.

2. Move the fulcrum closer to the resistance and take the same measurements.

• Measure the distance from the fulcrum to the re-sistance. ________in.___

• Measure the distance from the fulcrum to the ef-fort. _______in.____

• MA = effort arm length / resistance arm length. Calculate the MA of the lever.

• Which lever required the least amount of effort in order to move the resistance?

• Why?

1. The nutcracker is a second class lever. A second class lever has the resistance located between the fulcrum and the effort force. Try breaking the hard candy in your hand. Can you do it?

• Place the hard candy close to the nutcracker’s fulcrum and take the following measurements.

• Measure the distance from the fulcrum to the re-sistance. _________mm

• Measure the distance from the fulcrum to the ef-fort. ___________mm

• MA = effort arm length / resistance arm length. Calculate the MA of the lever.

Break the candy.

2. Now put another piece of candy in your nutcracker, but this time place the candy closer to the effort (your hand) and take the following measurements.

• Measure the distance from the fulcrum to the re-sistance. ___________mm

• Measure the distance from the fulcrum to the ef-fort. ___________mm

• MA = effort arm length / resistance arm length. Calculate the MA of the lever.

Break the candy.• Is it easier to break the candy when the resis-

tance is closer to or farther from the fulcrum? Why?

1. In a third class lever, the effort is between the ful-crum and the resistance. Use the tongs to experi-ment with the best location for the effort when pick-ing up an object.

• Is it best to be closer to or farther from the ful-crum?

• Why?

STATION 6: WHEEL AND axleA wheel and axle must be connected so that both turn one full revolution together. If the wheel turns and the axle remains stationary, it is not a wheel and axle machine.

The MA of a wheel and axle is the ratio of the radius of the wheel to the radius of the axle.

• Measure the radius of the wheel. ________mm___

• Measure the radius of the axle (it might be easier to measure the diameter and divide by two). _______________mm_____

• Calculate the MA of the wheel and axle if the effort is on the wheel. An example of this is a door handle.

• Using a wedge narrow enough for just the axle to rest on it, roll the machine down the in-cline. Measure how far the machine rolled be-yond the wedge. _____ft___

in

• Calculate the MA of the wheel and axle if the effort is on the axle. An example of this is a car’s wheel.

• Using a wedge surface with the same slope, roll the machine down the incline on the wheels this time. Measure how far the ma-chine rolled beyond the incline. ____ft___in_

• Which one moved farther?

• Which one moved faster?

• Why?

Conclusion

1) As you increased the number of pulleys, did the rope move a shorter or longer distance? Why?

2) Explain why it is easier to push or pull an object up an inclined plane than it is to lift the object straight up.

3.A screw is a combination of two simple machines. Which two simple machines are combined to make the screw?

4.Wedges can be used to split or cut something. Name two examples of wedges and explain why they make the task easier.

5.A wedge can also be used to hold something back (i.e., a door). Explain why a wedge would make the task easier.

6.Explain the difference between the wedge and the inclined plane.

7.Explain where you would put the fulcrum of a first class lever if you wanted to build a seesaw that you can ride with someone that weighs half as much as you.

8.List three examples of each type of lever.

First Class Lever Second Class Lever Third Class Leverteeter totter nutcracker tongs

balance scale stapler flat iron

catapult tweezers

9. Calculate the MA for the wheel and axle shown below.

10.What is the advantage of using a simple machine?

13. Is it possible to have a simple machine that does not provide mechanical advantage? Why or why not?