## Activity Simple Machines Explorations

Activity 5.3.3 Simple Machines Explorations Introduction Now that you know all about simple machines, let’s try building some of these amazing devices...
Author: Ralph Farmer
Activity 5.3.3 Simple Machines Explorations Introduction Now 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 advantage 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

Procedure As 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. © 2011 Project Lead The Way, Inc. PLTW Gateway – Science of Technology Activity 5.3.3 Simple Machines Explorations – Page 1

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

Pulley Pulleys 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. 1. Thread the rope around 1 pulley. Attach the weight to one end, the spring scale to the other end.   

How much weight are you moving? ______________ What is the value on the spring scale? ____________ Measure the length of rope needed to lift the weight from the table to the top pulley. Measure from the spring scale to the top pulley. _____________

2. Keep the rope around the pulley on the board or dowel rod and thread the rope through a pulley attached to the weight. 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.  

MA = Number of Supporting Ropes

What is the value on the spring scale? ____________ Measure the length of rope needed to lift the weight from the table to the top pulley. Measure from the spring scale to the top pulley. _____________ How is this different from using only one pulley?

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

© 2011 Project Lead The Way, Inc. PLTW Gateway – Science of Technology Activity 5.3.3 Simple Machines Explorations – Page 2

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

Length of sloped surface ________________ Highest point of inclined plane ____________ Figure MA = length/height: ________________ How much weight are you moving? ________ What is the value on the spring scale? ___________

MA 

L H

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

Length of sloped surface ________________ Highest point of inclined plane ____________ Figure MA = length/height ________________  How much weight are you moving? ________  What is the value on the spring scale? ___________ 5. Place the brick and cardboard on the table as shown. Record the following measurements (don’t forget your units).      

Length of sloped surface ________________ Highest point of inclined plane ____________ Figure MA = length/height ________________ How much weight are you moving? ________ What is the value on the spring scale? ___________ Which inclined plane required the least amount of effort to move the weight? Why?

© 2011 Project Lead The Way, Inc. PLTW Gateway – Science of Technology Activity 5.3.3 Simple Machines Explorations – Page 3

Which inclined plane had the highest MA?

Why?

Screw With 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? 6. 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 applied ________ (screwdriver handle)

Wood Screw

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

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 __________ 

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

7. 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 circumference you calculated in the previous

Drywall Screw

© 2011 Project Lead The Way, Inc. PLTW Gateway – Science of Technology Activity 5.3.3 Simple Machines Explorations – Page 4

question. ___________ Calculate the pitch of this screw. __________________ Calculate the MA of this screw. ___________________

 

Wedge The 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. 8.

Chisel #1:

 Length of sloped surface __________  Widest point of the wedge __________  Calculate the MA = Slope/Thickness _____________________________

MA 

L H

Lever There 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. 9. A first class lever has the fulcrum between the effort and resistance. Use the VEX pieces provided to build a seesaw.   

Measure the distance from the fulcrum to the resistance. ___________ Measure the distance from the fulcrum to the effort. ___________ MA = effort arm length / resistance arm length. Calculate the MA of the lever.

© 2011 Project Lead The Way, Inc. PLTW Gateway – Science of Technology Activity 5.3.3 Simple Machines Explorations – Page 5

10. Move the fulcrum closer to the resistance and take the same measurements.   

Measure the distance from the fulcrum to the resistance. ___________ Measure the distance from the fulcrum to the effort. ___________ 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?

11. In a third class lever, the effort is between the fulcrum and the resistance. Use the tongs to experiment with the best location for the effort when picking up an object. 

Is it best to be closer to or farther from the fulcrum?

Why?

© 2011 Project Lead The Way, Inc. PLTW Gateway – Science of Technology Activity 5.3.3 Simple Machines Explorations – Page 6

Wheel and Axle A 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. 12. Use the VEX pieces to build a wheel and axle mechanism. 

Measure the radius of the wheel. ___________

Measure the radius of the axle (it might be easier to measure the diameter and divide by two). ____________________ 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 incline. Measure how far the machine rolled beyond the wedge. ________

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 machine rolled beyond the incline. ________

Which one moved farther?

Which one moved faster?

Why? © 2011 Project Lead The Way, Inc. PLTW Gateway – Science of Technology Activity 5.3.3 Simple Machines Explorations – Page 7

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

2. Mechanical Advantage of a pulley system is figured by counting the number of supporting ropes. How much effort do you think is necessary to move a 100 lb block using 6 pulleys and 5 supporting ropes?

3. How much effort is necessary to move the same block if only 2 supporting ropes are available?

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

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

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

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

© 2011 Project Lead The Way, Inc. PLTW Gateway – Science of Technology Activity 5.3.3 Simple Machines Explorations – Page 8

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

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

10. List three examples of each type of lever. First Class Lever

Second Class Lever

Third Class Lever

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

12. 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?

© 2011 Project Lead The Way, Inc. PLTW Gateway – Science of Technology Activity 5.3.3 Simple Machines Explorations – Page 9