Simple Machines

Types of Simple Machines

How do machines make work easier? Machines make work easier by: multiplying the size of the force you exert (such as in this pulley system).

Machines also make work easier by: changing direction of the force. Example: A force on the rope downward, hoists the weight upward.

What are simple machines? A Simple Machine is a device that does work with one movement.

LEVERS A lever is a “bar” that is free to pivot, or turn at one fixed point. The fixed point is called a fulcrum.

The part of the lever on which the effort force is applied is called the effort arm. The part of the lever that exerts the resistance force is called the resistance arm.

First Class Lever

Examples of First Class Levers

Second Class Lever

Third Class Lever

PULLEYS: A pulley is a grooved wheel with a rope or chain that works something like a first class lever.

Comparing pulleys to levers

Pulleys can be FIXED or MOVABLE. The movable pulley has a greater mechanical advantage and therefore multiples the effort force by a greater amount.

More pulleys --More rope--Less effort

WHEEL AND AXLE Simple machine consisting of two wheels of different sizes that rotate together. The smaller wheel is usually called the axle. (Effort force – usually applied to larger wheel.)

Gears—modified wheel & axle The effort is applied to one gear. The gear ratio is found by dividing the radius of the effort ear by the radius of the resistance gear. (This is the ideal mechanical advantage for the gears.)

The SCREW A screw is an inclined plane wrapped in a spiral around a cylindrical post.

The wedge A wedge is an inclined plane with one or two sloping sides.