To maximize your cordless phone battery life, make sure to leave your phone off the base every once in a while until it is dead. Then leave it on the base until it is fully charged. You should leave your phone on the base for at least 24 hours to charge it fully. There is no need to avoid rechargeable batteries. They can save you significant amounts of money over time. Don't be scared off by the 'memory effect'.
In addition to being a great toy, the Slinky is an excellent device for creating and studying waves. A slinky can easily demonstrate the two basic types of waves, longitudinal and transverse. In a. longitudinal wave. the particles move parallel to the direction the wave is moving. In a. transverse wave. the particles move at right angles to the direction of wave travel.
A wave on a string is the classic example of a transverse wave. Each part of the string moves up and down while the wave moves from side to side. Transverse waves can not happen in gases because the perpendicular motion is not created by any force. A Slinky is a great way to visualize longitudinal waves. Each part of the Slinky moves from side to side, just like the wave itself. Sound waves are longitudinal pressure waves in the air. Water waves involve a combination of transverse and longitudinal waves. The water moves up and down, but also back and forth.