Work and Power

Compound Machines

A compound machine is a machine that consists of more than one simple machine. Some compound machines consist of just two simple machines. You can read below about two examples—the wheelbarrow and corkscrew. Other compound machines, such as bicycles, consist of many simple machines. Big compound machines such as cars may consist of hundreds or even thousands of simple machines.

Lever

A lever is a simple machine consisting of a bar that rotates around a fixed point. The fixed point of a lever is called the fulcrum. Like other machines, a lever makes work easier by changing the force applied to the machine or the distance over which the force is applied.

Machines

A machine is any device that makes work easier by changing a force. Work is done whenever a force moves an object over a distance.

Pulley

A pulley is a simple machine that consists of a rope and grooved wheel. The rope fits into the groove in the wheel, and pulling on the rope turns the wheel. Pulleys are generally used to lift objects, especially heavy objects.

Screw

A screw is a simple machine that consists of an inclined plane wrapped around a central cylinder.

Wedge

A wedge is simple machine that consists of two inclined planes, giving it a thin end and thick end. A wedge is used to cut or split apart objects. Force is applied to the thick end of the wedge, and the wedge, in turn, applies force to the object along both of its sloping sides. This force causes the object to split apart.

Wheel And Axel

A wheel and axle is a simple machine that consists of two connected rings or cylinders, one inside the other. Both rings or cylinders turn in the same direction around a single center point.

Inclined Plane

An inclined plane is a simple machine that consists of a sloping surface connecting a lower elevation to a higher elevation. An inclined plane is one of six types of simple machines, and it is one of the oldest and most basic.

Complex Pulley

Crane Pulley

Distance

Distance is the length of the route between two points. The SI unit for distance is the meter (m).

Efficiency

Efficiency is the percent of work put into a machine by the user (input work) that becomes work done by the machine (output work). The output work is always less than the input work because some of the input work is used to overcome friction. Therefore, efficiency is always less than 100 percent. The closer to 100 percent a machine's efficiency is, the better it is at reducing friction.

Energy

Energy is defined in science as the ability to move matter or change matter in some other way. Energy can also be defined as the ability to do work, which means using force to move an object over a distance. The SI unit for energy as well as work is the joule (J), or Newton • meter (N • m).

Fixed Pulley

Flagpole pulley

Third Class Lever

Hockey Stick

Mechanical Advantage

How much a machine changes the input force is its mechanical advantage . Mechanical advantage is the ratio of the output force to the input force, so it can be represented by the equation:

Simple Machines

Like all machines, they change forces and make work easier.

Actual Mechanical Advantage

Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Ideally, the device preserves the input power and simply trades off forces against movement to obtain a desired amplification in the output force.

Watt

Power has standard metric units of Joules per second, called Watts. W

Power

Power is work ( force x distance) divided by time which is a watt. Rate at which you do work. Power = Work divided by Time P= w/ t Work is in joules

Joule

Relationship between current and heat----wherever mechanical force is expended, an exact equivalent of heat is always obtained.

First Class Lever

Seesaw

Output Force

The force the machine exerts on a object.

Input Force

The force you put on the machine.

Ideal Mechanical Advantage

The ideal mechanical advantage is the change in input force that would be achieved by the machine if there were no friction to overcome. The ideal mechanical advantage is always greater than the actual mechanical advantage because all machines have to overcome friction. Ideal mechanical advantage can be calculated with the equation: Ideal Mechanical Advantage=InputDistance/Output Distance

Work Input

The input work times the input distance.

Work Output

The output work times the input distance.

Second Class Lever

Wheelbarrow

Input Distance

When a input force moves a machine a certain distance

Work

Work is the product of force and motion Work is done when a force acts on an object in the direction the object moves Work = Force × Distance

Movable Pulley

Zip-line pulley