Simple Machines Simple Machine a device that changes

Simple Machines

Simple Machine - a device that changes the size or direction of a force being used to do work.

WORK: You are doing work when you use a force to cause motion in the same direction. To measure the amount of work , multiply the force times the distance the object moved.

Work = F x D (work= force x distance the object moved) W F*D

Force (or weight) is measured in newtons Distance is measured in meters.

The unit of measure for work = Joule (J)

We can measure how much the force is changed by calculating mechanical advantage.

The force applied to do work is called the effort force (input).

The force that opposes motion is called the resistance force (output).

Actual mechanical advantage is the number of times a machine multiplies an effort force.

Ideal mechanical advantage does not consider friction.

There are six types of simple machines • • • Lever Incline plane Wedge Screw Pulley Wheel and axle

LEVER: The lever is a simple machine made with a bar free to move about a fixed point called a fulcrum.

There are three types of levers. • First class • Second class • Third class

A first class lever is like a teeter-totter or seesaw.

First class lever. Effort Force Fulcrum Resistance Force

A second class lever is like a wheelbarrow. The long handles of a wheel barrow are really the long arms of a lever.

Second Class Lever Resistance Force Fulcrum Effort Force

A third class lever is like a fishing pole. When the pole is given a tug, one end stays still but the other end flips in the air catching the fish.

Third class lever Effort Fulcrum Resistance

The mechanical advantage of a lever is calculated by dividing the Resistance force by the Effort Force. MA = RF/EF

INCLINED PLANE: An inclined plane is a simple machine with no moving parts. It is simply a straight slanted surface. (Ex. a ramp. )

A box with mass of 30 Newtons is lifted 10 meters to the top of a loading dock. 10 30

With the incline plane the effort distance is increased, and the effort force is decreased. 18 20

The effort force can be further reduced by increasing the length of the effort distance. 10 30

The mechanical advantage of an inclined plane is calculated by dividing the Resistance force by the Effort force. MA = RF/EF

The ideal mechanical advantage of an inclined plane is calculated by dividing the Effort distance by the Resistance distance. IMA = ED/RD

PULLEY: A pulley is a simple machine made with a rope, belt or chain wrapped around a grooved wheel. A pulley works two ways. It can change the direction of a force or it can change the amount of force.

A fixed pulley changes the direction of the applied force. (Ex. Raising the flag). A movable pulley is attached to the object you are moving.

The mechanical advantage of a pulley is calculated by dividing the Resistance force by the Effort force. MA=RF/EF

Power is the amount of work done in a period of time. Power is calculated by the following formula: P=W/t

Efficiency is the ratio of the work calculated by (output work/input work) * 100.

Compound machine a machine that is a combination of two or more simple machines.