ENERGYNotes and Key Concepts

Work An object’s motion is related to both

force and how the force acts. The quantity force X time = impulse The quantity force X distance = work

WORKTwo factors are

considered when work is done

1. The application of a force

2. The movement of something by

that force

The work done on an object by an applied force is the product of the force and the distance through which the object moved

Work=force x distance

W=Fd

POWER Power is the rate at which work is done Power=work done/time interval The unit of power is the joule per second, also

known as the watt One watt (W) of power is expended when

one joule of work is done in one second 1 Kilowatt (kW)= 100 watts 1 megawatt (MW) = one million watts

Metric System vs. United States In the metric system, automobiles are

rated in kilowatts In the U.S, we rate engines in units of

horsepower and electricity in kilowatts One horsepower (hp, is the same as

0.75 kW, so an engine rated at 134 hp is a 100-kW engine

Mechanical Energy is energy due to the position, or the movement of something

Mechanical Energy Potential

Potential energy is stored and held in readiness (a spring or stretched rubber band)

Examples: fossil fuels, electric batteries, and food

Gravitational potential energy= weight x height

PE=mgh

Kinetic Kinetic energy is

energy of motion It depends on

mass and speed of an object

Kinetic energy = ½ mass x speed2