The Doppler effect is the change in sound or light that occurs whenever there is motion between the source and its observer. The siren of the fire engine has a lower pitch as it moves away because the waves are now spread out causing a lower frequency and a lower pitch. High-frequency sound waves have a higher pitch and higher energy than low-frequency waves.
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For calculate frequency, lets applicate formula:

<u>Δ Being Δ</u>
f = Frequency = ?
v = Velocity = 144 m/s
= Wavelenght = 0,5 m
⇒ Let's replace according the formula:

⇒ Resolving

Result:
The frequency of that wave is <u>288 Hertz</u>
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The vacuoles because the plant's central vacuole is bigger.
Answer:
a. A baseball after it has been hit - not in free fall
b. A rock that is thrown in the air - not in free fall
c. The moon - free-fall
d. A paper airplane - not in free fall
e. A bird flying - not in free fall
Explanation:
- The free-fall is defined as the falling of an object due to the action of gravity. The object is not experiencing any other force neglecting the air resistance.
- If an object is in free-fall, the direction of its motion is directed towards the center of the earth. It does not have a horizontal component of velocity.
- If the body is under free-fall, but a centripetal force acts on it where it is equal to the gravitational force at that point. The object will have two components of velocity along the tangential line, perpendicular to the radius of the orbit.
a. A baseball after it has been hit - not in free fall according to point 1 & 2.
b. A rock that is thrown in the air - not in free fall according to point 1.
c. The moon - free-fall according to point 3.
d. A paper airplane - not in free fall according to point 1 & 2.
e. A bird flying - not in free fall according to point 1 & 2.