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Pulleys UNIT: PULLEYS OVERVIEW

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Pulleys UNIT: PULLEYS OVERVIEW Pulleys UNIT: PULLEYS OVERVIEW INTRODUCTION In this unit students will build on their knowledge of Simple Machines by building a pulley frame that can lift weights and also a block and tackle system that raises the arm of a Crane. STANDARD NCF ALIGNMENT SCIENCE • Idea of force-push or pull; change in speed, direction of moving objects MATHEMATICS • Conversion of units of length between smaller and larger units ENGLISH LANGUAGE ARTS • To be able to articulate individual/personal responses effectively • To use his/ her proficiency in English to explore and study other areas of knowledge through print and non-print media • To be able to narrate simple experiences, describe objects and people, report events to peers 1 Pulleys OVERVIEW CREYA OUTCOMES ANALYTICAL THINKING COLLABORATION • Analyzing information: data, ideas, or concepts • Contribution to team • Applying formulae, procedures, principles, or themes • Working with Others • Presenting multiple solutions, positions or perspectives • Time Management CREATIVE THINKING INFORMATION FLUENCY - JOURNALING • Ideation/Brainstorming • Format • Mechanics • Originality • Proper spelling and grammar • Flexibility in approaches INFORMATION FLUENCY - INFORMATION LITERACY PROBLEM SOLVING • Access the needed information • Define the problem • Identify Strategies • Propose solutions/Hypotheses • Implement the solution 2 Pulleys PREPARATION PROJECT 1: PULLEY FRAME PROJECT 2: PULLEY CRANE Overview: Overview: In, Pulley Frame, students will build a frame and lift a In the, Pulley Crane, students will use a block and load with pulley systems. tackle system to raise and lower a crane arm. Materials: Materials: 4 - Hinged Block Claw 4 - Tire 45 1 - Clip Axle 45 15 - Building Block 30 4 - Hub Nut 1 - Axle Coupling 2 - Building Block 15 4 - Hinged Block Claw 2 - Clip Axle 75 2 - Building Block 15 with 2 Pins 4 - Spacer Ring 1 - Crank Shaft 4 - Building Block 15x30x5 with Groove 9 - Building Block 15 with Bore 5 - Bearing Sleeve and Pin 15 - Building Block 30 2 - Building Block 7.5 4 - Bearing Sleeve 2 - Building Block 15 with 2 Pins 3 - Clip 5 1 - Bottom Plate 30x90 4 - Flat Hub Collet 1 - Mounting Plate 15x45 1 - String 2 - Clip Axle 30 1 - String Preparation Tips: Preparation Tips: Be gentle with raising and lowering the load on the pulley frame. Rough usage Pay attention to which pulley the string rests on. with the pulley system can break the frame. 3 Pulleys BACKGROUND About Pulleys How do you raise a flag on a tall flagpole, without machine is the number of times a machine multiplies standing on top of it? Most flagpoles use a pulley. A the effort, and is the ratio of the output force to the pulley is a simple machine made with a rope, belt, input force. A moveable pulley rises and falls with the or chain wrapped around a grooved wheel or similar load that is being moved and creates a mechanical device. Pulleys are generally used to raise, lower, or advantage. A combination of fixed and move a load. A pulley changes the direction of the moveable pulleys in a block and tackle pull, or effort. When you pull down on a flagpole’s also creates mechanical advantage and rope, the flag will rise. A single pulley makes a job reduces the amount of effort needed to pull up a load. Block and tackle system allows heavy object to be lifted with less force. In a block and tackle, the rope must be pulled a greater distance as it winds through several sets of pulleys. The trade-off for less effort is more rope pulled. seem easier by letting you pull with the force of gravity instead of lifting against it. For example, you If you are pulling down on a rope are asked to raise a 50 kilogram weight. If you tie a on a block and tackle system, the 1 2 rope to the weight and try to raise it, you have to pull mechanical advantage is equal to up something weighing 50 kilograms. If you run the the number of ropes supporting the rope around a pulley, you are pulling down; it seems load. Count each end of the rope as slightly easier because you can use your own weight a separate rope. as a counterweight. A fixed pulley does not rise or fall with the load being moved, and does not create a For example, two rope ends support a moveable mechanical advantage. pulley which is connected to a 100 kilogram weight. The mechanical advantage is 2 and in this situation, One of the properties of a simple machine such as the an effort force of 50 kilograms will lift a resistance pulley, is that is it can be used to magnify the force force of 100 kg. applied to a task. The mechanical advantage of a 4 Pulleys BACKGROUND Terms BLOCK AND TACKLE A block and tackle is a tool often used to lift heavy or hard to reach objects. It consists of two basic parts. The block is a pulley or set of pulleys fitted in a frame. The block is usually attached to a stationary object. The tackle is the rope or cable that runs through the block and anything else needed to make the machine work. Some tackles, like the one in the picture, use moving pulleys as well as the rope. The rope will move through the block and, together, the block and tackle can be used to help one person lift a lot more than they could without it. FIXED PULLEY A fixed pulley is a pulley that is fixed into one place. MOVEABLE PULLEY A moveable pulley is a pulley that moves along a rope or chain as it is pulled. It is the opposite of a fixed pulley. PULLEY A pulley is a wheel with a groove around the edge. Pulleys can be used as a simple machine to change the direction of a pulling force. By throwing a rope or chain over a pulley, you can lift something up by pulling down. MECHANICAL ADVANTAGE Mechanical advantage is the upper hand you gain when you use a mechanical device or machine to help you multiply the amount of force you can transmit. Mechanical advantage is expressed mathematically as a ratio or fraction. The top number of the fraction is the force the machine puts out to perform the work you’re trying to do. This top number is therefore called the output. The bottom number of the fraction is the force you have to put into the machine to make it do the work, and we call this number the input. “WOW” Exercises The following is a class demonstration that allows students to experiment with pulleys. 1. You will need a broom handle or other rigid dowel, duct tape, a length of rope, and a liquid detergent jug filled with water. 2. Ask students to lift the jug straight up using the rope and broom handle. Have students share their results. 3. Tape the ends of the broom handle down between two desk tops or other appropriate surfaces. Tie one end of the rope to the broom hand and loop the rope through the jug handle. Loop the rope around the top of the dowel, back through the jug handle and loop again around the top of the dowel again. The jug handle will act as a movable pulley. 4. Have students lift the jug by the free end of the rope. Have students compare the effort between lifting the jug, and using the pulley system to lift the jug. 5. Compare the amount of rope used lifting the jug with one loop around the dowel, and the amount of rope used with the two loops. Does one system use more rope than the other? 5 Pulleys PROJECT 1: PULLEY FRAME Materials 15 - Building 2 4 - Building Block 15x30x5 1 - Bottom 4 - Bearing 4 - Hinged 2 - Building 1 - String Block 15 Block 30 - Building Block 15 with Groove and Pin Plate 30x90 Sleeve Build In this project, you Place a Bottom Plate 1 will build a frame and 3 30x90 over the pairs of experiment with lifting Building Block 15x30x5 a weight with a single with Groove and Pin. pulley system. You will compare it to lifting the weight with a multiple pulley or block and tackle system. Start by building the Position two Building 2 frame supports. Take four 4 Block 15s with 2 Pins Building Block 15x30x5s on the frame support with Groove and Pin and and mount five Building connect two of them Block 30s on each of the together to form two sets Building Block 15s with 2 of two. Pins. 6 Pulleys PROJECT 1: PULLEY FRAME Place Building Block 15 on Place two Hinged Block 5 each of the two columns. 8 Claws on top of the Fix two Building Block 30s Building Block 30. between the two Building Block 15s. Attach a Hinged Block 6 Claw with Bearing Sleeve beneath each of the two Building Block 30s. These Bearing Sleeves and Hinged Block Claws will serve as fixed immovable pulleys in a block and Insert a Bearing Sleeve tackle. Set the frame 9 into each of the Hinged aside. Block Claws. Start the moveable pulley 7 piece of the block and tackle. Place a Building Block 30 on top of two vertically placed Building Block 30s. 7 Pulleys PROJECT 1: PULLEY FRAME Place the moveable pulley 10 component between the upright posts of the support frame. Finished. Run a string from one 11 of the Bearing Sleeves on the moveable pulley component up 4 to one of the Bearing 2 3 Sleeve components on the frame. Run the string back down to the 1 second Bearing Sleeve on the moveable pulley component and up and over the second Bearing Sleeve component on the frame.
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