Energy Does Work (1961)

foreign [Music] here they are playing on a swing that's Billy pushing Joe they're waiting for their father to come home from work here comes dad he's tired today because he's been working hard at his job Billy is a little tired too from playing on the swings with Joe that's what Billy tells dad when he sees him but Dad says if this is what you've been doing then you've been doing work too work no pushing someone on a swing is play how can play be work dad will tell him how in science the word work has a special meaning whenever something is moved we can say that work is being done when Billy pushes Joe he makes Joe move because something is moved work is done if we think of work in this special way we can find many examples of work being done all about us here is work being done both the boy and his bicycle are being moved and here is work being done the girl does work as she lifts her doll to the slide and when the doll slides down work is being done work is done when a toy tractor is moved or when a toy car is moved then work is also done when a real car is driven when a merry-go-round is turned work is done and work is also done when the horses are moved up and down when a sailboat is blown across the water or when sand or gravel falls out of a truck work is being done work is done whenever something is moved but whenever something is moved there has to be something that makes it move this something is called Energy the energy that moves Joe on the swing comes from the muscles of Billy's arms Anytime work is done energy is needed energy to move the boy and the bicycle comes from the muscles of the boy's legs the energy that moves the toy tractor is in its wound up Spring when the spring unwinds it releases energy that turns the treads on the tractor an unwinding spring also makes the car move and so work is done a real car is moved by its engine energy from gasoline runs the engine the engine turns the wheels that make the car go long ago we used the energy of animals to move heavy things and to do other work today powerful engines do much of this work for us gasoline or diesel oil supplies the energy for some engines work is done by electricity too the energy of electricity moves this real train and this toy train too the energy of electricity is used to turn the blades of a mixer and to move the parts of an electric clock whenever something is moved work is being done so energy is needed but is that really true look over there on the slide when a girl lets her doll slide down we know work is being done but it doesn't seem that any energy is needed to make the doll move but energy is needed although in a slightly different way from what Billy has been seeing when the girl lifts her doll above the ground to the slide she uses energy this energy is stored in the doll as long as the doll is above the ground it is this stored energy that is used to do work when the doll slides down Billy thinks he understands any time an object is raised the energy that is used to raise it is stored in the object when the object comes down again the energy is used and work is done energy is stored in the same way in a swing when it is at rest the swing is near the ground but when it is moving it goes high above the ground it is the energy from Bill's arms that raises the swing let's suppose we could stop the swing right here at its highest point now energy is stored in the swing because it has been raised this energy is used when the swing comes down again All Around Billy are examples of other ways that energy can be stored energy to move the toy tractor is stored in its wound up Spring the energy that is used by the boy to wind the spring will remain stored in it until the spring unwinds our muscles like the spring in the tractor store energy too we all have stored energy in our bodies which we use when we move things when we do work the bicycle Rider also uses the energy which is stored in his muscles but how does energy get into our bodies there's how it comes from food food contains energy we get this energy from food when it is eaten and digested energy from food is stored in our bodies we use this energy when our muscles or other parts of our bodies need it food is a kind of fuel for our bodies machines need fuel too a car runs on gasoline energy is stored in the gasoline when the gasoline Burns in the engine its stored energy is released and it can do work this lawnmower also uses gasoline to furnish the energy to do work this diesel locomotive uses oil another fuel that supplies energy airplanes also make use of the stored energy in fuel and so do motorboats much work is done by machines that use the energy that is stored in fuels Billy wants to learn more about work and energy and he begins to think about the many examples of work being done we can notice work being done all about us too work is done when the clouds are moved by the wind work is done when you Coast down a hill on a sled at home work is being done when steam moves the valve of a pressure cooker or when running water washes food from a plate even walking is work we use energy from our muscles to move ourselves look around and see what you can discover about energy and the work it does [Music]