Answer:
Speed at which the bat have to fly is 90.895 m/s away from the human (listener) in positive direction.
Explanation:
Given:
Frequency of the bat that is source here, 
= 25.3 kHz = 25.3 * 10^3 Hz
Frequency of the listener (human), 
= 20 kHz = 20*10^3 Hz
We have to identify how fast the bat have to fly in order for a person to hear these chirps .
Let the velocity of bat that is source is "Vs" and "Vs" = "Vbat".
Doppler effects formulae :
- When the source is receding (moving away)
- When the source is approaching
- Speed of sound in
the air (medium), 
Using the above formula and considering that the bat is moving away so that the human can listen the chirps also 
as listener is stationary.
⇒ ⇒ 
Re-arranging in terms of Vs.
⇒ 
⇒ 
⇒ 
⇒ 
m/s
The speed at which the bat have to fly is 90.895 m/s away from the human (listener) in positive direction.
Answer:
Force and Change in velocity
Explanation:
The contact time is the exact same, as they have hit eachother, rather than something.
The force is how hard they hit eachother, and due to the weight of each object, and the size, the mosquito has much less force.
The change in velocity is also unequal. While the mosquito gets squished, and is now getting thrown in the other direction, the truck is almost completely uneffected, and it's movement stays the same.
Green plant - cow - human - mosquito
Answer a is one of keplers 3 laws
The initial mass fraction of the spacecraft that must be burned and ejected to achieve an increase in speed is 0,00219 m/s
<h3>What fraction of the initial mass of the spacecraft?</h3>
Increase the speed: Vf-Vi = 2.2 m/s
Speed of aircraft: Vr = 400 m/s
Speed of ejected products: Vrel = 1000 m/s
The answer is:
So, the initial mass fraction of the spacecraft that must be burned and ejected to achieve an increase in speed is 0,00219 m/s
Learn more about spaceship speed fraction brainly.com/question/28256735
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