The question is asking to calculate the object's speed v1, v2, v3 at the certain time is the given of the problem, in my calculation, I would say that the speed would be 2m/s, 1.5m/s, 0.22m/s. I hope you are satisfied with my answer and feel free to ask for more if you have question and further clarification
Answer:
the formula is efficiency = output / input × 100%
Wavelength = speed / frequency
(345 m/s) / (20,000 Hz) = 0.017 m
Do u know Chinese ?if yes I can explain to u easily
