1. ENERGY Notes and Key Concepts

2. 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

3. WORK Two 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

4. 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

5. 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

6. 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