Answer:
37.545 m/s
Explanation:
f' = Actual frequency of horn = 269 Hz
f = Observed frequency of horn = 290 Hz
v = Speed of sound in air = 343 m/s
= Speed of second train = 13.7 m/s
= Speed of first train
From Doppler effect we have

The speed of the first train is 37.545 m/s
Answer:
It cancels recoil.
Explanation:
For each action there is an equal an opposite reaction.
The principle of conservation of momentum tell us that if a single spore were ejected the fern would suffer a recoil from it. This recoil would take energy and speed from the spore. But if they are ejected in pairs the recoil is canceled and all the energy is transferred to the spores resulting in higher speeds.
I believe it's Mercury, because the only other option would be Pluto and it's not even considered a planet anymore
Hope this helps
B. If all plants are watered at least once a day then they will all grow at least 1 cm a day.
All plants grow at different rates.
Hope this helps! XD
Well, the reason behind this is because water depth (I assume you're talking about water/liquid) increases the pressure because of the weight and volume of the water above. I hope this helps! ~Mia