Answer:
Mistakes, chaos theory.
Explanation:
Weather forecast refers to the application of technology and science in predicting what the condition's of an atmosphere would be at a particular time in a given location. Keyword here is "Predicting."
To accurately "predict" the weather, observation data needs to be collected from weather stations across the world. The data collected from the stations are too complex such that they can only be processed by supercomputers.
It is important to note that supercomputers used to predict weather are liable to make mistakes because the enormous challenge of weather forecasting is more than their capabilities.
In addition, there is a concept known as chaos theory. It explains how very small changes in initial weather conditions can change the final results. No thanks to chaos, meteorologists would not be able to predict weather accurately.
This is the reason why the world still suffers from the incidence of surprise rain, storms and other weather events that could be devastating.
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Answer:
Velocity, v = 0.239 m/s
Explanation:
Given that,
The distance between two consecutive nodes of a standing wave is 20.9 cm = 0.209 m
The hand generating the pulses moves up and down through a complete cycle 2.57 times every 4.47 s.
For a standing wave, the distance between two consecutive nodes is equal to half of the wavelength.

Frequency is number of cycles per unit time.

Now we can find the velocity of the wave.
Velocity = frequency × wavelength
v = 0.574 × 0.418
v = 0.239 m/s
So, the velocity of the wave is 0.239 m/s.
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