WORK, POWER, & EFFICIENCY

WHAT is Work? Work occurs when a force makes an object move. In order to do work two things must occur. First, you must apply a force to an object. Then, the object must move in the same direction as the applied force. You do work on an object only when the object moves as a result of the force you exert. A force that does not make an object move does no work.

WHAT is Work? Work Not Work

Work and Energy Doing work on an object transfers energy to the object. This is important because it helps them predict how an object will act when a force is applied. Moving objects have kinetic energy. When work is done on an object, the work transfers energy to the object. The added energy is the kinetic energy of the moving object.

WORK & ENERGY

HOW IS WORK MEASURED? More work is done when the force is increased or an object is moved a greater distance. Work is equal to the force of a push or a pull multiplied by the distance the object is moved. Work= force x distance The force must act in the same direction as the motion. If the force is expressed in newton and the distance is expressed in meters, the units for work are newton-meters; or as they are called joules.

How Work is Measured?

Power = energy transferred What is Power? The amount of work done per unit of time, or work divided by time, is called power. Power is expressed in joules per second, (J/s). One joule per second is also known as a watt (W). This is the standard unit of power. Light bulb labels indicate the power of the devices use per second. The more power a light bulb has, the brighter the light is. Horsepower also measures power. A horsepower is equal to 746 W. Calculating power: Power = energy transferred time

Efficiency = output work x 100 WHAT IS EFFICIENCY? The efficiency of a machine is the ratio of the output work to the input work. Efficiency is calculated using the equation below. Efficiency = output work x 100 input work Because output work is always less than input work, a machine’s efficiency is always less than 100 percent.