You didn't actually include the speed of sound. But it doesn't matter for this question. If the trumpeter and the listener are on the same moving sidewalk then the distance between them is not changing. The Doppler shift only happens when the distance between the source and the Observer is changing. So the Listener hears the same 290 Hertz that the trumpeter is generating.
Negative:
plants and animals risk habitat loss as they have had exposure to dangerous byproducts of technology.
if someone creates something dangerous, then humans can inhale harmful chemicals in air pollution and it also consumes resources that are non-renewable
positives:
you can use technology to help the environment, through the use of recycling, purification of water and air to prevent pollution and contamination. for the second one you could say that technology has stopped the habitats from dying
hope this helps in some way :)
Answer:
The flow area at the location where the Mach number is 0.9 is 25.24 cm²
Explanation:
Here we have for isentropic flow;

Where:
A = Area of flow = 36 cm²
M = Mach number at section of = 1.8
k = Specific heat ratio = 1.4
A* = Area at the throat
Therefore, plugging the values we get

Therefore, A* = 36/1.439 = 25.01769 cm²
Where the Mach number is 0.9, we have

Therefore A = 25.020× 1.009 = 25.24 cm²
The flow area at the location where the Mach number is 0.9 = 25.24 cm².