Today’s Wonder of the Day was inspired by Isaac from Fenton, MI. Isaac Wonders, “How do cranes work?” Thanks for WONDERing with us, Isaac!

If you've ever seen a tall building being built, then you've probably been amazed to see those tall machines used to lift heavy materials and equipment to great heights. What are we talking about? The crane, of course!

In many large cities, cranes are as much a part of the skyline as tall buildings themselves. But how do such tall, skinny machines lift so much weight? There's nothing magic about them. Cranes make great use of some basic scientific principles to do their important work.

Cranes are commonly found at construction sites around the world. Mobile cranes move about easily, lifting heavy objects shorter distances and helping to put together larger tower cranes.

Tower cranes stay in one place and can lift large loads to great heights. Without cranes, it would be very difficult to lift heavy construction materials and equipment, such as concrete, steel beams, generators, and torches.

The tall, vertical part of a crane is known as the mast. To support such heavy weights at great heights, the mast must be supported by a large, heavy base. For example, the mast of a tower crane is usually bolted to a large concrete pad that can weigh as much as 400,000 pounds!

At the top of the mast, you'll find the slewing unit, which consists of a gear and motor that allows the crane to rotate. Three other important parts can be found on top of the slewing unit.

The long horizontal working arm, called the jib, uses a trolley to help carry the load. The shorter machinery arm contains the crane's motors, along with large concrete counter weights that help balance the load. Finally, the electronic controls used to operate the crane can be found inside the operator cab.

Despite the advanced technology used in cranes, they actually make use of a combination of simple machines to multiply force to lift extremely heavy objects. In balance-style cranes, the crane's beam is balanced at a point, called the fulcrum, to allow it to lift heavy objects with a relatively-small force. In this way, the crane's beam acts as a simple lever to multiply force.

Cranes also make use of another simple machine — the pulley — to multiply force to lift heavy objects with smaller forces. In tower cranes, for example, the force required to lift heavy loads is diminished by utilizing a system of multiple pulleys.

Using the scientific principles behind simple machines, such as the lever and the pulley, cranes are able to multiply smaller forces to lift incredibly heavy loads to great heights. How heavy? It's not uncommon for large cranes to lift loads of nearly 40,000 pounds!

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