A range of constrained speeds
Teaching Guidance for 14-16
A range of speeds and constraints
The speed of travel is often constrained by the physical environment of the object. The constraint may be technological, material, or even more fundamental. It's a good idea to have a number of these to hand, and perhaps to base some discussion around which category the example falls into, and whether anything we can do might change the speed.
Teacher: Work on the first Thames 1200-foot tunnel took 16 years and two months, an average rate of progress (allowing for the seven-year lay-off) of only 4 inches a day. This was a good measure of how sorely the project tested the technology of the day.
Teacher: Row a boat through water, and the waterline length of the boat will set your top speed. A longer rowing boat will always beat a shorter rowing boat in a race.
Teacher: There is an ultimate speed limit: nothing can exceed that speed. So the very structure of the universe itself seems to provide a kind of constraint. This speed also happens to be the speed of light in a vacuum. That makes light (and other electromagnetic radiations) rather special.