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上传于：2016-03-24

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    188宝金博页面版: Quick and Easy Simple Machine Experiments to Share …

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    内容提示： Quick and Easy Simple Machine Experiments to Share with Your Kids By Aurora Lipper Pulleys and levers are simple machines, and they make our lives easier. They make it easier to lift, move and build things. Chances are that you use simple machines more than you think. If you have ever screwed in a light bulb, put the lid on a jam jar, put keys on a keychain, pierced food with a fork, walked up a ramp, or propped open a door, you've made good use of simple machines. Mechanical advantage is like using ...

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    Quick and Easy Simple Machine Experiments to Share with Your Kids By Aurora Lipper Pulleys and levers are simple machines, and they make our lives easier. They make it easier to lift, move and build things. Chances are that you use simple machines more than you think. If you have ever screwed in a light bulb, put the lid on a jam jar, put keys on a keychain, pierced food with a fork, walked up a ramp, or propped open a door, you've made good use of simple machines. Mechanical advantage is like using brains instead of brawn (using your mind instead of brute muscular strength). With pulleys and levers, you use your 'mechanical advantage' to leverage your strength and lift more than you normally could handle, but it comes at a price. You trade force for distance. When you are using a pulley system, you can thread it up to lift ten people with one hand. Here's the trade-off: You will have to pull ten feet of rope for every one foot they rise up. To figure out the mechanical advantage in a pulley system, count the number of strings in your system. (This will make much more sense after you build the pulley experiments). If there are seven strings, you can pull with seven times your normal strength. With levers, it's a little easier to figure out the advantage, mostly because there are no strings to count or get tangled up. You're just using fulcrums. (Think of the pivot point in a see-saw.) By moving the fulcrum of levers around, you can dramatically change how much you can lift. Let's get started! Second Class Levers Lay a 2" x 4” x 10' length of wood on the ground. Have a smaller kid sit in the middle of the beam, holding on as you (the larger kid-adult) lift up one end. Leave the other corner resting on the ground – you can even ask a big adult to sit on it so it doesn't slide around. This end is your fulcrum. Have the kid move further back toward the fulcrum, and lift up the beam again. Experiment with both the kid position and effort you exert to lift the beam. Find out where you need to sit to have the kid lift you. They usually can, if you sit in the right position!

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