Final answer:
Speed itself is not a proportional characteristic without a comparison context. In physics, a proportional relationship between quantities implies one changes directly as the other, based on a constant. The concept of instantaneous speed shows that speed can change independently of other factors.
Step-by-step explanation:
When considering if an ostrich running at a speed of 43 miles per hour is proportional, we must define what it is being compared to. Proportionality in this context could mean comparing the ostrich's speed with another time or distance, though speed itself is not inherently a proportional characteristic without a context for comparison. In physics, we often deal with ratios or proportions when discussing relationships between different physical quantities. A proportional relationship would imply that as one quantity increases or decreases, the other does so in a directly comparable manner, based on a constant of proportionality.
Speed is the distance traveled per unit of time, and it can vary independently from other quantities. It does not represent a proportional relationship on its own. For example, the speed of a car can vary widely over the duration of a trip, influenced by numerous factors such as traffic conditions, road inclines, or the car's mechanical performance. This is evident in the notion of instantaneous speed, which is described by a car's speedometer at a specific instant, illustrating that speed can change independently and is not necessarily proportional to another factor unless explicitly stated.
Acceleration is another key concept in physics which can relate to speed. For instance, a car moving in a circle at a constant speed is not accelerating in terms of its speed, but it is accelerating in terms of its direction. This illustrates how a condition, where speed is constant while acceleration is not zero, is possible.