Additional specifications and requirements

¶ … Machines & Marble Drop

The Simple Machines and Their Use in an Inclusive Marble Drop Toy

A force is required to move an object. The force applied in and through the distance moved is the work done. Machines are generally used to change the force necessary to move an object, though the overall work is the same neglecting wasted friction.

There are fundamentally six simple machines out of which more complicated machines are composed. They are the inclined plane, the wedge, the screw, the lever, the wheel and axle, and the pulley.

The inclined plane allows one to push an object up and along the plane with less force than directly raising the object. The wedge is one or two backed-to-back inclined planes. it's used to pry two things apart. One applies a force to advance the wedge which splits wood or raises a heavy object perpendicular to the applied force's direction. The screw is a narrow inclined plane, called a thread, wrapped around a cylindrical core. Turning the screw core advances it as the thread slides through material or along a guide depending on the screw's purpose.

The lever is a stiff rod that rotates about a pivot point called a fulcrum. Forcing down on one end of the lever causes the other end to rise while lifting an object due to the pivoting action of the fulcrum. The greater the forcing end's distance is from the fulcrum compared to that of the object's distance, the less the force needed to lift the object.

The wheel and axle is composed of a larger radius disk with a smaller radius axle fixed through its center. As the two parts turn in unison, the longer distance traversed at the disk's radius corresponds to a shorter distance at the axle's radius. The force needed to turn the assembly at a given torque (twisting strength) is least at the wheel's rim compared to the force needed at the axle's rim in inverse relation to their respective radii.

The simple pulley uses a rope riding along the rim of the wheel and axle to reverse the force applied to an object on one end of the rope from that force applied at the other end of the rope. If the rope can be run through two or more pulleys, the force applied at one end of the rope to lift the object on the other end can be reduced.

What's interesting is that the mechanical advantage that each simple machine may offer for reducing the force needed to move an object comes at the expense of having to apply the force through a longer distance. So a short motion of a force produces a longer motion of the object.

A marble drop machine is toy that makes use of simple machines to move one or more marbles through it from top to bottom. The idea of this toy is to create a lot of motion of its parts and the marbles to watch. And that motion is produced with the marbles that literally fall through it. The force on the marble is its weight. Because it can roll and fall, it can be made to roll down a plane and drop onto a lever's end to produce a force to move the other end.