Machines do work

tom has just received a crate of sweet juicy apples that came all the way from uncle George's fire the crate is fastened with nails but tom is so excited that he's trying to open it with his bare hands in just a minute tom why do it the hard way you can do it much more easily if you use this machine wire is a machine of course we know that many machines are big and complicated like these but we should also know that some machines are very simple up honor is a machine so is an or and a nutcracker any tool that helps to make our work easier can be called a machine a bottle opener is a machine because it helps you to remove the cap more easily a pair of oars help you to row a boat and if you've ever tried cracking a walnut with your bare hands you know how useful a nutcracker can be these three machines are shaped differently but they all work in pretty much the same way because they are examples of one type of simple machine which is called believer the lever is usually a rod that rests on a support like a seesaw the support is called the fulcrum if we push down on one end of the rod we can lift a heavy weight at the other end one man can lift another man very easily with the help of a machine like this if we move the fulcrum closer to one end of the rod one man can lift several men just as easily by pushing down on the long end he lifts a heavy weight on the short end in this way the lever can be used to perform many difficult tasks where a lot of force is needed remember how we use the crowbar to force open the crate of apples the crowbar is a lever and the edge of the crate is a fulcrum push down on the long end of the lever and close the board sometimes the fulcrum of a lever is at the very end as in the bottle opener and sometimes two levers have the same fulcrum a nutcracker for example here the fulcrum is the hinge at the end of the Nutcracker another simple machine that helps us do work is the wheel and axle a small force on the wheel will move a heavy weight on the axle a steering wheel works this way a small force on the wheel steers a heavy automobile very easily a pencil sharpener is a form of wheel and the hexyl machine tool although it may not look like one here instead of a whole wheel we simply use one spoke of the wheel the spoke is the handle which turns the axle and the axle turns the sharp blades inside this is a model of a windlass a wheel and axle machine that is used to lift heavy weights have you ever seen a man load a barrel on a truck by rolling it up a big plank a plank used in this way is another kind of simple machine which is called the inclined plane you can perform an experiment to see how the inclined plane makes our work easier in order to lift this heavy book from the floor to the chair you must use a force of more than 50 ounces but with the help of an inclined plane you can bring the book up to the chair with a force of about 25 ounces when you ride up the hill or a mountain you are using an inclined plane to get to the top sometimes too inclined planes are put together to help us do work an axe is an example of a double inclined plane so is a knife and you know what kind of a machine a screw is it's simply an inclined plane that's twisted around you probably know that this machine is called a pulley a pulley is just a wheel with a rope or chain wrapped around it with this machine a man can move an object from one place to another without having to move very far himself when mrs. Jones drives close she doesn't have to walk all over the yard a pulley saves her a great many sets if we put a number of pulleys together like this we can use them to lift very heavy objects in this way painters can raise their heavy scaffolds without much effort you have learned about four simple machines which helped to make our work easier believer of reel and axle the inclined plane and the pulley most of the machines in the world are made of these simple machines put together in different ways for example how many simple machines can you find in this big complicated one and here is an easy question what kind of machine helps to raise our flag [Music]