Island 1 IQ Key Level 2 Mighty Machines

Leverage and Mechanical Advantage:

POP students will explore the concepts of leverage and mechanical advantage.

Work is a product of force applied over a distance, and is a measure of energy applied to an object. It is expressed by the following formula:

Force x Distance = Work

If we want to perform more work, we can increase the force, increase the distance, or increase both.

If we want to perform a fixed amount of work (like lifting a 50-pound weight 1 foot off the ground), we can increase the distance over which work is performed and use less force to accomplish the task. This is called leverage.

How Does Leverage Work?

Lifting a 100-pound weight one foot off the ground requires 100 foot-pounds of total work.

50 pounds x 1 foot = 50 foot-pounds

We could simply pull it straight up if we were strong enough. If we wanted to use less force, we could use a lever.

A lever is a simple machine to help us trade distance for force. Here we applied a force of 10 pounds over 5 feet to do the same amount of work.

10 lbs x 5 ft = 50 foot-pounds

This requires us to move farther to lift the object the same distance as before (5 ft vs. 1 ft), but it will take less force (10 lbs vs. 50 lbs).

When machines help make work easier by trading distance for force, we call this mechanical advantage. The lever shown above had a mechanical advantage of 5:1 (because we used 1/5th as much force to accomplish the same amount of work).

Parts of a Lever:

All levers have three parts.

• Load – This is the work we want to do. A load is anything that provides resistance to the lever. The elephant is the load. 

• Fulcrum – This is the pivot point for the lever, meaning the lever tilts around it. The green triangle is the fulcrum.

• Effort  – This is where we apply force. If you wanted to lift the load, you would apply effort by pushing down on the lever.

Gears and Mechanical Advantage:

Just like the lever, gears allow us to use less effort to do the same work. Gears increase the distance over which we apply a force.

Gears can create mechanical advantage when we combine different size gears with different circumferences. The outer edge of a larger gear has to cover more distance than a smaller gear in order to complete a full rotation. In other words, one full rotation of a larger driver gear will cause its smaller driven gear to rotate more than one full rotation.