{{:forces:girl-motion-790x50.jpg|Forces & Motion Banner}} ====== Q1: COMPARING WEIGHTS ON A PULLEY: ====== The purpose of this task is to help you understand how forces act in a pulley system. === CORE CONCEPTS: === A single fixed pulley only changes **the direction** of a force - not the amplitude (the amount) of force. In our experiment we will see how a pulley can change the direction of a force so that two weights pull against each other. ++++ Q2. CLICK HERE TO SEE / HIDE STUDENT FLIP RESOURCES:| {{youtube>9T7tGosXM58?640x360|Simple machine - Pulleys}} **Video: Simple machines - Pulleys** * IF UNABLE TO ACCESS YOUTUBE VIDEO (requires Flash) TRY:[[http://viewpure.com/9T7tGosXM58|Simple machine - Pulleys]] ---- {{youtube>qlI9GlUUlbg?640x360|Simple machines - The Wheel & Axle}} **Video: Simple machines - The Wheel & Axle** * IF UNABLE TO ACCESS YOUTUBE VIDEO (requires Flash) TRY:[[http://viewpure.com/qlI9GlUUlbg|Simple machines - The Wheel & Axle]] ---- [[http://www.physicsclassroom.com/PhysicsClassroom/media/interactive/AtwoodsMachine/index.html|{{:learn:forces:quiz:atwoods-machine-640x360.jpg|Atwoods Machine - Interactive Problem Solving}}]] Click on weights and blocks to set up experiments - you can also left-click and drag items on left-hand side of simulator. ---- [[https://phet.colorado.edu/sims/html/balancing-act/latest/balancing-act_en.html|{{:learn:forces:quiz:balance-phet-640x360.jpg|Balance Lab}}]] Click and drag items to create experiments and to find out how it works - menu bar is at bottom of the simulator screen. More [[https://www.youtube.com/watch?v=I-1LI2tWtNg|about levers]]. ---- ++++ ++++ Q1. CLICK HERE TO SEE / HIDE EXTRA STUDENT FLIP RESOURCES| ** Reminder: ** * A force is a push or a pull. * Forces [[http://www.physicsclassroom.com/class/newtlaws/Lesson-3/The-Big-Misconception|do not cause motion]]; forces cause acceleration. * Identify what forces are affecting the weights. * Identify the locations where forces are acting & what direction they are acting in. \\ ** AN EXAMPLE EXPERIMENT: ** This is an experiment to help you understand the difference between a simple lever (like a 'see-saw', 'teeter-totter' or balance bar) and a simple pulley (like a hook that has no friction). An example **observation** might be: * Equal weights placed at equal distances on a horizontal balance bar (see-saw) remain in balance. An example **[[http://www.sciencemadesimple.com/scientific_method.html|hypothesis]]** might be: * When two weights are placed the same distance from a fulcrum the weights/balance will not move. * When one weight is moved closer to the the fulcrum, one end of the balance will fall. * I expect the result will be the same when the position of the weights is changed, both for the pulley and for the balance. An example **experiment to test my hypothesis** (using alternative strategies and the resources provided in the student wiki): - Set up the balance and pulley as shown in Fig 1. - Place the two EQUAL weights at EQUAL distance from the fulcrum (mark 6) - Shorten the length of one arm by moving one weight closer to the fulcrum (eg. mark 4) - Describe what happens to the weights. Does one weight go up, go down or stay the same? {{:learn:forces:quiz:q1-balance-pulley-level.jpg|Balance Level}} ** Fig 1. Weights set at equal distances on the balance (see-saw) and on the pulley ** NEXT, consider this: - Set up the balance and pulley as shown in Fig 2. - First, position the two EQUAL weights at EQUAL distance from the pulley - Now shorten the length of one arm (rope) by moving one weight closer to the pulley - Describe what happens to the weights. Does one weight go up, go down or stay the same? {{:learn:forces:quiz:q1-balance-pulley-tilted.jpg|Balance tilted }} ** Fig 2. Weights set at unequal distances on the balance (see-saw) and on the pulley ** * Q: Are the results of both of these experiments the same? * A: Place your answer below - in the box titled 'Post your comments here:' ---- ++++ ++++ CLICK HERE FOR INFORMATION ABOUT HOW THE DISCUSSION SECTION WORKS| For each of the QUIZ question pages, there is a DISCUSSION section (at the base of each page). Authorised visitors may enter comments and reply to discussions. Entering simple text content should be intuitive. 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