Pulley

Our next simple machine is a pulley (here by Evilnurn). A simple pulley changes the direction of a force transmitted by a cable as that cable moves around the circumference of the pulley. For instance, you could attach a rope to a rock and loop the rope over a pulley above you. If you pull down with a force of ten pounds, the result will be an upward force of ten pounds on that rock.


If you loop back and forth between two or more pulleys, you create a block and tackle (here by Louise Dade). This gives you a mechanical advantage. For instance, if there are two parallel stretches of rope, as in the model below, if you apply ten pounds of force in pulling the rope, twenty pounds of force will be exerted to lift the load. BTW, you never get something for nothing - you have to pull the rope twice as far to get double the force.

Lever

I was going to move on to the next simple machine, but Bobofrutx just posted this great example of a lever.

Wheel and axle

Next up in our look at simple machines is the wheel and axle. As with the lever, there is a relationship between the amount of force applied along the edge and the radial distance. Therefore a large wheel can be turned with relative ease, and yet be used to lift a large weight, as seen in this medieval crane by Stephle59.

Simple machine: lever

A simple machine is a mechanical device that changes the direction or magnitude of a force. Classical and Renaissance scientists defined six different ones. A lever (here by Linda Hamilton) is a rigid rod that pivots on a point called the fulcrum. In a class 1 lever, when a downward force is applied on one side of the fulcrum, an upward force results on the opposite side.



It also makes a difference how far the point of force application is from the fulcrum, as the actual term to be considered is torque, defined as the amount of force times the distance. The longer the lever, the greater torque can be produced, so that very large objects can be moved, as shown here by Ringleader. Archimedes supposedly said he could lift the earth if he were given a long enough beam and a place to set the fulcrum.

LEGO math fun

LEGO is great for teaching kids math concepts. I've used stacks of Duplo bricks to practice addition - i.e. 'put the stack of two bricks together with the stack of three bricks, and how tall is the tower?' And I've previously noted helping my daughter learn her 2x multiplication table. Here Erin from the So you call yourself a homeschooler blog is using stacks of bricks to teach fractions.

Apollo 13

CustomBricks has a look back at the Apollo 13 service module as the astronauts leave in the command module for their return to Earth.

Gear up

A gear is a simple machine, where two or more wheels have teeth, or cogs, that fit together so that when one turns, the teeth fit together so that the other turns as well. In this way, rotational torque is transferred from one axle to another. These axles can be parallel to each other, or, as in this case by Legohaulic, at an angle. If the gears have different diameters, they will rotate at different speeds.

Argon

Argon (here by the One and Only Mr R) is an element with the atomic number 18. It is a noble gas, which means it does not enter into reactions to form compounds with other elements (hence the name, derived from the Greek word for lazy). Argon is the third most abundant gas in the earth's atmosphere, after nitrogen and oxygen.