WheelThe wheel is the main part of this simple machine. It only touches the ground at the bottom of the wheel which means that there is less friction acting on the load. When there is less friction, everything is easier to move! Think about how slippery ice is. It is slippery and easy to slide on because there is very little friction acting on your shoes. Same thing with wheels! Also, the bigger the wheel is the better! With a large wheel, the force is spread out over even more area making the wheel able to carry a ton more weight! Look at some examples below.
![]() Look how big the wheels are on this tractor! These wheels work the same way as the wheels on your bicycle or the wheels on toy cars. The only difference is that these wheels have a big motor spinning their axles to make the wheels do even more work!
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AxleThe axle is the rod that is attached to the center of the wheel. This spins as the wheel rotates which allows for all kinds of possibilities! The axle is what allows the wheel and axle to do so many helpful things.
![]() How can this doorknob be a wheel and axle? The wheel is the part that you turn with your hands to spin the axle that is on the inside of the doorknob. This axle acts like a lever on the bolt inside the door and makes it move out of the way so that you can open the door!
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Use the arrows to navigate through the simple machines or you can pick any one you want by clicking on the images above.