Some simple and random facts.

Why do runners start from different positions in the same track?

When tracks races are run in lanes, the runners on the outside cover more distance than those on the inside as they come around the bend. To ensure that everyone travels the same distance, the runners start at staggered points. It is 200 and 400 meter sprint in which all runners flat out in different lanes. The hundred meter dash is run on a straight lane. Longer races of several laps where runners have plenty of time to bunch up on the inside lane do not need staggered starts.

How submarines work?

When a submarine wants to dive, its ballasts tanks are flooded with seawater, and the hydroplanes are set to direct the craft downwards. Once it is submerged, the hydroplanes are readjusted to control the angle of drive. When the submarine has reached the right dept the hydroplanes are set to horizontal position and small auxiliary tanks are flooded. The opposite happens when the vessel surfaces. Ordinary submarines use battered powered electric motors while they are underground and diesel engines when cruising on the surface. Nuclear submarines use heat from a nuclear reactor on board to drive a steam turbine. Nuclear submarines can sub merge for a long time.