REVIEWREVIEW

Work Power and MachinesWork Power and Machines

What Is Work?What Is Work?

Key ConceptsKey Concepts

Work is done on an object when the object moves in thWork is done on an object when the object moves in the same direction in which the force is exerted.e same direction in which the force is exerted.

The amount of work done on an object can be determinThe amount of work done on an object can be determined by multiplying force times distance.ed by multiplying force times distance.

Power equals the amount of work done on an object in Power equals the amount of work done on an object in a unit of time.a unit of time.

What Is Work? What Is Work?

Key TermsKey Terms workwork joulejoule powerpower

How Machines Do Work?How Machines Do Work?

Key ConceptsKey Concepts A machine makes work easier by changing at least oneA machine makes work easier by changing at least one

of three factors. A machine may change the amount of of three factors. A machine may change the amount of force you exert, the distance over which you exert your force you exert, the distance over which you exert your force, or the direction in which you exert your force. force, or the direction in which you exert your force.

A machine’s mechanical advantage is the number of tiA machine’s mechanical advantage is the number of times a machine increases a force exerted on it.mes a machine increases a force exerted on it.

To calculate the efficiency of a machine, divide the outTo calculate the efficiency of a machine, divide the output work by the input work and multiply the result by 10put work by the input work and multiply the result by 100 percent. 0 percent.

How Machines Do Work?How Machines Do Work?

Key TermsKey Terms machinemachine input forceinput force output forceoutput force input workinput work output workoutput work mechanical advantagemechanical advantage efficiencyefficiency

Simple MachinesSimple Machines

Key ConceptsKey Concepts

There are six basic kinds of simple machines: the inclined plane, tThere are six basic kinds of simple machines: the inclined plane, the wedge, the screw, the lever, the wheel and axle, and the pulleyhe wedge, the screw, the lever, the wheel and axle, and the pulley. .

You can determine the ideal mechanical advantage of an inclined You can determine the ideal mechanical advantage of an inclined plane by dividing the length of the incline by its height. plane by dividing the length of the incline by its height.

The ideal mechanical advantage of a wedge is determined by diviThe ideal mechanical advantage of a wedge is determined by dividing the length of the wedge by its width.ding the length of the wedge by its width.

The ideal mechanical advantage of a screw is the length around tThe ideal mechanical advantage of a screw is the length around the threads divided by the length of the screw.he threads divided by the length of the screw.

Simple MachinesSimple Machines The ideal mechanical advantage of a lever is determined by dividiThe ideal mechanical advantage of a lever is determined by dividi

ng the distance from the fulcrum to the input force by the distance ng the distance from the fulcrum to the input force by the distance from the fulcrum to the output force.from the fulcrum to the output force.

You can find the ideal mechanical advantage of a wheel and axle You can find the ideal mechanical advantage of a wheel and axle by dividing the radius of the wheel by the radius of the axle.by dividing the radius of the wheel by the radius of the axle.

The ideal mechanical advantage of a pulley is equal to the numberThe ideal mechanical advantage of a pulley is equal to the number of sections of rope that support the object. of sections of rope that support the object.

Most of the machines in your body are levers that consist of bonesMost of the machines in your body are levers that consist of bones and muscles. and muscles.

The ideal mechanical advantage of a compound machine is the prThe ideal mechanical advantage of a compound machine is the product of the individual ideal mechanical advantages of the simple oduct of the individual ideal mechanical advantages of the simple machines that make it up. machines that make it up.

Simple MachinesSimple Machines

Key TermsKey Terms inclined planeinclined plane wedgewedge screwscrew leverlever fulcrumfulcrum wheel and axlewheel and axle pulleypulley compound machinecompound machine