Engineer III Simple Machines

Transcription

1 Harford District 2014 Cub Scout Day Camp June Knights of the Roundtable Engineer III Simple Machines Station Volunteer s Guide

2 Thank you for being a station volunteer! The stations are the heart of camp and truly provide our scouts with an opportunity to try out a new skill (or build on one they know) while having a great time. Our volunteers knowledge and enthusiasm is what makes our camp great! To make running the station easier, please take some time to read through the station guide. While, what is being covered at the station needs to remain as outlined so that the scouts earn the correct achievements, how it is covered is only one of many methods. If you find a better way to accomplish the requirements or if the method we have outlined doesn t seem to be working please feel free to change it! This is only a guide do what works best for you and the scouts coming to your station. One other thing to keep in mind some stations will be visited by all ranks. That means you may have 6 year olds through 11 year olds and may have to simplify or intensify the methods to meet the skills and knowledge of all the scouts. Thanks again we are glad to have you as part of Harford Day Camp! Station Procedures The first station begins at 10:15 on Monday and 9:15 other days so you have some time! We ve tried to only schedule 2 dens at a time (max. 24 boys) but, there may be times when you have 3. Consult your station schedule so you will know who to expect and when. Greet dens as they arrive. Many will have a den cheer, ask to hear it! Once all the dens arrive or the start time has come, begin going through the procedures for the station. It is very important that you start and end on time! Each time slot lasts 45 minutes. If a den arrives 10 minutes late, they CANNOT stay 10 minutes past the end of the station that would make you and them late for the next station. If a den doesn t get finished, suggest they come back during a break or take the remaining activity with them to work on at the den. Execute the station with energy and enthusiasm! Let the scouts do as much for themselves as possible. It doesn t need to be perfect, they just need to Do Their Best! Don t forget the beads. Each scout earns a bead at every station for participating. Beads can be given to the den leader for distribution. Once the den is finished, begin resetting for the next group. Close the station at the end of the day by packing/organizing the supplies and cleaning and disposing of all trash. Let the Program Director responsible for the station (either Tiger/Wolf/Bear or Webelos) know if supplies are running short!

3 Station Overview Scouts will be introduced to six different types of simple machines and will engage in five demonstrations using various simple machines. The Station Leader will engage the scouts in a discussion about how simple machines work and will explain how certain simple machines are used in everyday life. Core Values: Cooperation, resourcefulness and perseverance Set-up: Open the bins and set up 4 areas for the scouts to see first-hand simple machines in action. Area #1, Simple Block and Tackle Demonstration (in Webelos book) This simple apparatus shows how a block and tackle increases power. You need two lengths of broomstick and a length of clothesline. Fasten one end of the line to one of the sticks. Wrap line loosely around both sticks as shown.

4 Area #2 Lever (See Saw): For this activity, create a see saw using the 2x6 board and a fulcrum object (1 foot lengths of stacked wood). See figure. Area #3 Pulley. For this activity, there will be 4 different pulley s set up. The fixed, moveable and compound pulleys will be demonstrated and the make your own pulley will be a hands-on activity. Fixed Pulley: - Find the bag labeled 'Fixed Pulley' - Have a Boy Scout tie the included rope with the pulley on it to the support beam in the pavilion. (this may already be done for you) - There should be longer rope with a small wooden block at the end in the labeled bag. The block is to serve as a 'stopper' to hold the weight. Thread this rope through the hole on the free weight and pull all the way through to the stopper. Then thread the rope on to the pulley. - This set up should look like the diagram later in this guide. Moveable Pulley: - Find the bag labeled 'Moveable Pulley' - Have a Boy Scout tie a longer rope to the support beam in the pavilion. (This should already be done) - Thread a pulley onto the rope (as in the diagram later in the guide). - Attach the weight to the looped end of the rope using the wooden 'stopper'. Compound Pulley: - Find the bag labeled 'Compound Pulley' - Have a Boy Scout tie the ropes to the support beam in the pavilion to resemble the compound pulley configuration later in this guide. (This should already be done)

5 - Attach the weight to the looped end of the rope using the wooden 'stopper'. Make your own pulley: Have 4 ropes tied to a support pole in the pavilion. Supply each rope with a weight and a pulley. After each group has completed this station, reset the supplies so that the next group can assemble the pulley. Area #4 Inclined Plane if time permits: Create an inclined plane using the 6 length of 2x6 wood. Support the one end of the board on an elevated surface (we used a weighted plastic tub). Break-Down 1) Return all materials to the bins. 2) Please assure that all bins are closed tightly and place under the tent for the night. 3) In the event that rainy weather is expected, please place bins in the Crouse Building. Station Objectives: Each scout will complete the following requirements: Engineer Requirement 8: Science Pin Requirement 4: Make a simple crane using a block and tackle and explain how the block and tackle is used in everyday life. Use these simple machines to accomplish tasks: lever, pulley, wheel-and axle, wedge, inclined plane, and screw. 1. Greet the scouts as they arrive 2. Explain to the scouts the topic of the station. Say: This station is all about machines. Emphasize that the scouts should not touch anything unless instructed to do so.

6 Does anyone know why we use machines? We are going to learn about Simple Machines. Simple machines are devices that help people do work. Work has a specific meaning in physics, but basically is refers to how much effort is required to make things move. (Work = Force x Distance) Simple machines help make our work easier. They allow us to change the size and direction of an applied force. There are six basic types of simple machines. Each type provides a desired mechanical advantage so that work can be done more efficiently and effectively. Even the most complex machines designed by engineers today are a combination of one or more of the six known simple machines. Overview of 6 Types of Simple Machines Ask if anyone knows 1 type of simple machine. As the scouts provide responses point to an example set up at the station. See if they know any examples before asking for another type. Here are the types: 1. Wheel and Axel: has a larger wheel connected to a smaller cylinder rod called an axle. The axle goes through the wheel, allowing for the wheel to turn. A wheel and axle makes it easier to move things from place to place. Examples bike, wheelbarrow, doorknob, steering wheel, skate board 2. Inclined Plane: An incline plane is a flat surface that is higher at one end, such as a ramp, that can be used to alter the effort and distance involved in doing work, such as lifting or lowering loads. The trade off is that an object must be moved a longer distance than if it was lifted straight up, but less force is needed. Examples: handicap accessible Ramp, slanted road, slide, path up a hill 3. Lever: A lever is a rod or board that pivots on a point called a fulcrum. Pushing down on one end of the lever results in the upward motion of the opposite end of the fulcrum. Example: hammer (fulcrum = wrist, see saw (fulcrum = the middle point), tweezers, nutcracker, fishing rod, crowbar, bottle opener. 4. Screw: A Screw is an inclined plane that is wrapped around a cylinder. Examples of screws include: fasteners that are used to attach wood or metal; lifting screws that are used to lift heavy objects and dig holes; and bolts that are used with nuts to keep things together. More Examples: Key ring, spiral stairs, jar lid, clamp 5. Wedge: A wedge is actually 2 inclined planes put together. A wedge can be used to split things apart (axe) or hold things (door stop). More Examples: knife, wooden yard stake

7 6. Pulley: Pulleys are used to change the direction and/or the magnitude of an applied force. Examples: crane, flag poles, clotheslines, mini-blinds Compound Machine: Next, discuss compound machines. Say: If all of the ones we talked about are simple machines, what is a compound machine? A compound machine is two or more simple machines working together to make work easier. Example: Hold up a Circle Compass. Looks like a small machine, but it is a complex machine using multiple types of simple machine principles: Lever arm rotating around the top fulcrum Screw used to hold the arms in place while making them moveable Wheel and axel you rotate the wheel to make the arms move Wedge the pin at the end to hold it in place 3. Split your scouts into 2 groups. Have the groups rotate through the demos. Before you send them to the demos, give rules: Do not touch any of the equipment unless instructed to do so, pay attention to the speaker and the specific rules at each station. Area #1, Simple Block and Tackle Demonstration (in Webelos book) Have two scouts grasp the sticks and apply gentle outward force try to keep them apart while another den member pulls on the line. This works especially well if the bigger scouts hold the sticks and the smaller scout pulls the rope. He should be able to pull the sticks together no matter how the others try to keep them apart. Make sure scouts do not pull too vigorously on the ropes, and avoid rubbing the rope against anyone s hand.

8 Rope puller stands behind and slightly to the side of one of the holders, so that rope is perpendicular to broomstick. The role should go under the arms of a holder, but not rub against his side. Pulling rope should be parallel to the ground. Holders need to keep broomstick parallel to ground and parallel to each other. Do not let the rope rub their hands. Discussion: The purpose of this activity is to show the mechanical advantage of a block and tackle pulley. This type of pulley system distributes a load (the force of the scouts pulling on the broom) over a greater number of ropes (the number of times wrapped around the stick), and thus allows for a high mechanical advantage, making it easier to pull the two scouts together. However, even though less force is needed, the pulling force must be carried over a longer distance (a greater length of rope must be pulled). Area #2 Lever Demonstration (See Saw): All of the scouts will participate in this demo at some point. Rules: only step on the seesaw when you are told, do not step off until told to do so. Keep finger out from underneath. Have Youth Volunteers stand right next to scouts on the seesaw. If they need balance, have them hold the Youth Volunteer s shoulder. First get 2 volunteers. First have one boy stand on one end. Then have the other scout stand opposite to see if he can lift the other. Have them step off. Get another volunteer to see if 1 boy can lift 2 boys. If not, ask boys what they can do to make this possible (move the fulcrum). Add more scouts. Repeat with various combinations and other volunteers. FYI: There are three classes of levers: First class has the fulcrum placed between the effort and the load. Example: Crowbar, see saw Second class has the load placed between the fulcrum and the effort. Example: Nutcracker Third class has the effort placed between the load and the fulcrum. Example: Tongs Area #3 Pulley Demonstration For this demonstration, the scouts will see 3 different types of pulley configurations: Fixed, Moveable, and Compound (Block and Tackle). They will also have the chance to lift a 5 lb. or

9 10 lb. load using each configuration. Discuss the differences with each. Emphasize that the scouts should not touch anything unless instructed to do so. Discuss proper technique for pulling the rope: hand over hand for up and back. Do not let the rope go and do not let it run through your hands. At the end they will have a chance to set up their own pulley system. Pulley #1: Fixed Pulley: For a fixed pulley, the force to lift the 10 lb weight is the same as if you didn t have a pulley at all. You still need to apply about 10 lbs. of force to lift the weight. However, the direction of the force has changed. You pull down instead of lifting up. Pulley #2: Moveable Pulley: The force required to lift the 10 lb. weight is only about half of what you would need without a pulley. Explain this by holding the rope on either side of the weight, with the weight hanging in the middle. Explain that half of the weight is felt on your left hand and half is felt on your right hand. So with this pulley, about half of the weight is supported by the rope section from the pulley to the ceiling, So the side you pull fells only about half. Thus the weight is distributed evenly between the 2 ropes above the pulley. (you can add that it is not exactly half due to friction of the rope on the pulley) So, even though this system helps relieve some of the lifting weight, you still need to apply your force in the upwards direction.

10 Pulley #3: Compound Pulley (Block and Tackle) Ask if the scouts recognize the 2 types of pulleys used in this configuration: Both a fixed and a moveable. Thus it is called a compound system, because you have taken 2 types of pulleys and combined them to work together. Because you have the moveable pulley, the force required to lift the 10 lb. load is only about half of what you would need without a pulley. Since you have the fixed pulley up above, the force can be applied in a downward motion. Again, friction plays a role so that the force is not exactly half, and the more pulleys, the more friction. Show that even though it is easier to pull, you will need to pull more length of rope to raise the weight (about double). So, the force is easier, but the length is longer. You can have them measure the rope length required to raise the weight 3 to show this (should be about 6 of pulled rope). Pulley #4 - Make your own Pulley: Ask the scouts to work together (2 per rope preferably) to thread the rope on the pulley to put together a moveable pulley configuration. Area #4 Inclined Plane if you have time: An incline plane is a flat surface that is higher at one end, such as a ramp, that can be used to alter the effort and distance involved in doing work, such as lifting or lowering loads. The trade off is that an object must be moved a longer distance than if it was lifted straight up, but less force is needed. Examples: Ramp, slanted road, slide, path up a hill Using the bowling ball, have the scouts test the effort required to move the bowling ball by lifting, versus the effort using the inclined plane (both up and down). Emphasize that they should not let go of the ball, just guide it up and down. Background Information that May be Helpful: Additional background information can be found in the supplemental folder in the station bin.