Physics

Barometer measures air pressure.

When air is cooled and water vapour condenses to form water liquid, energy is released as water particles ‘give up’ some of their energy in order to slow down and move closer together again. The same is true when liquid water freezes to become ice. This energy is also called latent heat.

When a pail of water is swung in a vertical circle, the water does not fall out at the top of the loop when the speed is great enough. At every point in the circle the water tries to fall vertically out due to the force of gravity g but also tries to move in a straight line due to its circular motion.

The indexes of refraction for diamond, air and glass are, respectively, 2.42, 1.00, and approximately 1.50, depending upon the composition of the glass. Light travels slowest in diamond.

Surface tension is responsible for the shape of liquid droplets. Although easily deformed, droplets of water tend to be pulled into a spherical shape by the cohesive forces of the surface layer. In the absence of other forces, including gravity, drops of virtually all liquids would be perfectly spherical. The spherical shape minimizes the necessary “wall tension” of the surface layer according to Laplace’s law.

Saturn is mainly composed of the lightest two gases known, hydrogen and helium. It is the only planet in our solar system whose density is less than water.

A hygrometer is an instrument used to measure relative humidity. Humidity is the measure of the amount of moisture in the air. A psychrometer is an example of a hygrometer.