Engineers who design battery operated devices such as cell phones and mp3 players try to make them as efficient as possible and engineer test a cell phone and finds out the battery supplied 10000 joules of energy to make 5500 joules of output energy in the form of sound and light for the screen how efficient is the phone

a high pressure system is a dense air mass that is usually cooler and drier than the surrounding air. a low pressure system is a less dense air mass that is usually wetter and warmer than the surrounding air.

in general, areas that experience high atmospheric pressure also experience fair weather. low pressure systems can cause the formation of clouds and storms. air usually flows from areas of high pressure to areas of low pressure..

show the wavelengths of a wave. show the crests of a wave.