Molecules and polyatomic ions are formed by covalent bonds.
Answer:
b) 472HZ, 408HZ
Explanation:
To find the frequencies perceived when the bus approaches and the train departs, you use the Doppler's effect formula for both cases:

fo: frequency of the source = 440Hz
vs: speed of sound = 343m/s
vo: speed of the observer = 0m/s (at rest)
v: sped of the train
f: frequency perceived when the train leaves us.
f': frequency when the train is getTing closer.
Thus, by doing f and f' the subjects of the formulas and replacing the values of v, vo, vs and fo you obtain:

hence, the frequencies for before and after tha train has past are
b) 472HZ, 408HZ
What do you mean? I'm confused... You need to put the rest of the question
Answer:
leaf and a balloon is the correct answer
We'll look at two properties:
1. The variation in temperature
2. The material's heat transfer coefficient
By taking an example;
Use a circular rod made of a certain material (for example, steel) that is insulated all the way around.
One end of the rod is immersed in a huge reservoir of 100°C water, while the other is immersed in water at 40°C. The cold water is kept in an insulated cylinder on both sides. The temp of the chilly water is measured using a meter as a time - dependent.
Conclusion of experiment;
- Heat is transferred from a hot location to a cooler region.
- Whenever heat is applied to a body, its thermal power rises, and its temperature rises.
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