Final answer:
The question primarily involves Physics, as it relates to the forced oscillation of a rectangular speed limit sign by wind, the tension in power lines influencing wave speed, and the kinetic energy of a car when subjected to winds at different angles.
Step-by-step explanation:
The topic of oscillation caused by wind relates directly to Physics, focusing on the understanding of waves, harmonic motion, and aerodynamics. In regards to the rectangular speed limit sign oscillating, when wind passes by such a structure, it can cause the sign to undergo vibrations or oscillations due to the aerodynamic forces acting on it. This is an example of forced oscillation, where the repetitive force of the wind can make the sign resonate at its natural frequency.
The tension in power lines, which is relevant when discussing waves and their speed, is provided by the mechanical stretching of the lines. This tension ensures that the power lines are taut and is a key factor in determining the speed of mechanical waves along the lines, much like the tension in a guitar string affects its pitch.
When analyzing the effect of wind on a moving car, it is important to consider the direction and speed of the wind in relation to the car's direction of travel. At a 30-degree angle, the wind will impart some kinetic energy to the car, providing additional forward momentum. Conversely, at a 135-degree angle, the wind is effectively blowing in the opposite direction of the car's motion, which could decrease the car's kinetic energy and slow it down.
For the plane scenario, a combination of crosswind and head-wind will result in a total velocity that is less than the plane's velocity relative to the air mass. Additionally, this combination will likely change the plane's direction of travel. Understanding these effects is critical for both safety and fuel efficiency in aviation.