Lesson 2 - Inclined Plane and Pulley
Lab Packet: PDF | Open Office | Word Document
After investigating the work accomplished by applying force, students will be able to:
- Describe 2 of the simple machines, the inclined plane and the pulley.
- Describe how each of these machines can make work easier.
- Represent data in a table and calculate mechanical advantage.
- Construct graphs showing relationships of force to effort.
- Make predictions using data in the graph.
- Recognize appropriate uses of machines and advantages of combining the inclined plane and pulley.
- Recognize relationships between inclined plane and wedge.
- Recognize examples of inclined planes and pulleys in their surroundings.
- Basic math skills.
- Graphing skills.
- Units of measure for force Newton (N), and distance meter (m) and centimeter (cm).
- These lessons build on basic concepts covered in Simple machines activity One.
- Work = Force X Distance through which force moves.
- Direct and indirect relationships.
- Computer lab with Internet connections or a single machine and suitable projection equipment. We recommend a Pentium class computer. (166 MHz, with at least 32 MB ram).
- Browser with the latest Flash Player. For questions/assistance write firstname.lastname@example.org
- Student Packet - This is a printable version of the lab materials (Instructions, tables, graph formats, and questions/problems) where students can record their lab.
- Invitation to learn - Small lab carts and spring scales, board pieces for inclined planes, books, weights, ladder and can or object to carry, broomsticks or heavy dowels, 10 or 23 ft. pieces of rope (nylon cord), chinning bar or access to goal posts, pulley sets.
Introducing the inclined plane can include awareness of any ramps in your building, delivery or general access, the slope of curbs at the cross walks, the use of stairways versus ladders to access upper stories. Once you have given a few of these examples students should be able to generate a list of the more obvious examples.
Taking into account any liability or problems of access to ladders, a fun demo is to have a student or students climb a ladder carrying a paint can or other object at varying angles from near vertical to a comfortable angle. Discuss results and ask for theories to explain why there was a difference in difficulty with increased slope.
If you have access to spring scales and carts, ramps can be created by resting a piece of wood on a stack of books. Students can collect data by recording the scale readings using various weights in the carts, adjusting height and length of the ramp. This data could be used for general discussion or generation of graphs or charts. Different student groups could be assigned to change only one variable then share their results and conclusions with the class.
Introducing the pulley could be done by playing a tug of war game using a length of rope (nylon cord works well) and two broomsticks or heavy dowels.
Place the 2 broomsticks on a surface parallel to each other about a foot apart. Tie the rope to one stick and wrap the rope around the two dowels 3 to 5 times. The object of the game is to have 2 students pull the sticks apart as another student attempts to pull them together by pulling on the end of the rope. A variation of this game can be played using a broomstick and a chinning bar or the cross bar of the goal posts. The rope is wrapped around the broomstick and the supporting bar and the object is to lift students hanging onto the broomstick. As the students vary the number of times the rope is wrapped around the sticks, they get a real hands on experience with the "power" of the pulley as a machine. This generates much more enthusiasm than pulley sets and weights. This also helps emphasize the importance of the number of supporting ropes as opposed to the "little wheels".
If you have pulley sets and weights this could be used here but would probably be better used as a follow up activity.
Discussion during the invitation to learn activities and any predictions you request will give a good assessment of student background knowledge. Each lab worksheet calls for prediction before completing the activity.
Directions for teaching the lab:
Depending upon your lab time constraints you may choose to have students collect all computer needed data while on the computers and then complete the calculations and graphs after lab. This activity may be taught as three separate lessons. Lesson 1: Inclined planes, Lesson 2: Pulleys, Lesson 3: Cooperation which is a shorter activity showing how simple machines can be combined to enhance the mechanical advantage
Each student should have a lab packet to record their data and responses.
Invite students to proceed to simple Machines 2 lab activity where they will be introduced to and given a definition of an inclined plane and then proceed to the story line of the activity. They are asked to generate a list with their partner, frequently in the lab students are asked to discuss their answers and predictions with their partner. This icon will prompt them to these discussions
Monitor this activity to help students share their ideas and value their partner's ideas as well.
In this lab they are dealing with the problem of transporting massive building stones to an elevated site and then lifting the stone into position. An inclined plane is used to push these stones to the building site, the students are able to adjust the length of the inclined plane and they are given measurements of length of ramp and effort force needed to move the stone. They will record this data in their student packet and answer questions to interpret this information. Use of complete sentences in answering questions is repeatedly emphasized to insure students are able to express underlying ideas completely and to reinforce their understanding of the concepts. It is important that you discourage the use of single word or phrase answers. Discussion with their partner is encouraged.
Students transfer this data to table 2 in their lab packets where they calculate work done on each test.
The relationship between the length of the ramp and force needed is represented by completing a graph. Students are asked to label their graphs, you may want to guide them to an appropriate scale or you could just assign line values. There are seven rows and the maximum force is 3500 N, the length divisions will be determined by the lengths they chose to test.
The wedge connection following the lever activity investigates the similarities between the inclined plane and the wedge.
The second part of this lab deals with the pulley. A pulley system is developed and used to lift the stone into position on the wall. They will test four different configurations of pulleys and record the # of supporting ropes, effort applied to the rope, distance the end of the rope was pulled and the distance the stone was lifted.
Using this data, students are asked to calculate work and mechanical advantage. They also graph this data and are asked to interpret relationships shown by the pattern of points plotted.
The challenge following this activity could be used as an assessment tool.
The final activity combines the inclined plane and a pulley system. Students can adjust both the inclined plane and number of pulleys. Students calculate the MA of each component of the system and of the system as a whole showing the cumulative nature of machines in combination.
This lesson will introduce students to the inclined plane and the pulley. They will be able to calculate work input, work output, mechanical advantage and interpret relationships by plotting points on a graph.
Questions answered as the activities are completed will check for basic understanding. The challenge following the pulley activity could be used as an assessment tool.
Due to the variance in class time, computer access, and student abilities, it may be difficult to estimate the time needed to complete these activities. If time is limited students can complete data collection in the computer lab and complete the graphing and interpretive activities at another time.
- Using the tug of war idea, you could have competitions. (Pulley Olympics)
- Lab pulley sets and carts could be used to create original combinations to accomplish various tasks. Ie: lift an object using the least input force, transport an object using given restraints (# of pulleys, length of rope, length of board, etc)
- Create a display of constructed or collected examples of inclined planes, pulleys, or combinations.
- Challenge students to create a Rube Goldberg invention using simple machines to accomplish a simple task. Refer to www.rube-goldberg.com for background information and contests, etc.
- We've found another, more recent website that we love here: http://fantasticcontraption.com/ While we prefer sites like ASPIRE which are free from advertising and support curriculum, this 'game' is definitely a wonderful resource to problem solve and build complex machines in a nicely programmed physics simulator.
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