Neglecting friction and air resistance, the first hill must be built 4 times higher than it is now.
We will hear the sound of siren of frequency 1553.4606 Hz.
<h3>What is Doppler Effect?</h3>
The apparent change in wave frequency brought on by the movement of a wave source is known as the Doppler effect. When the wave source is coming closer and when it is moving away, the perceived frequency changes. The Doppler effect explains why we hear a passing siren's sound changing in pitch.
according to Dopplers Effect,
![f'=[\frac{v + v_{0} }{v - v_{s} } ]f](https://tex.z-dn.net/?f=f%27%3D%5B%5Cfrac%7Bv%20%2B%20v_%7B0%7D%20%7D%7Bv%20-%20v_%7Bs%7D%20%7D%20%5Df)
![f'= [\frac{700+68.1}{700-94.8} ]* 1224](https://tex.z-dn.net/?f=f%27%3D%20%5B%5Cfrac%7B700%2B68.1%7D%7B700-94.8%7D%20%5D%2A%201224)
the frequency would be 1553.4606 Hz.
to learn more about Doppler Effect go to - brainly.com/question/9165991
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They are helium nuclei, which consist of two protons and two neutrons. The net spin on an alpha particle is zero. They result from large, perilous atoms via a process called alpha decay.
<h3>What is
helium nuclei?</h3>
- The nucleus of the helium atom also understood as the α-particle, includes two protons and two neutrons, encompassed by two electrons.
- Alpha particles are helium nuclei with two protons and two neutrons attached. The development of their high mass and an electrical charge is their inability to infiltrate as deep as other particles such as protons and electrons.
- Particle beams contain α (alpha)-particles, β (beta)-particles, neutron beams, etc. α-particles are helium middles consisting of two protons and two neutrons that have lived removed at high speed, while β-particles are electrons removed from a nucleus. Particle shafts also include neutron beams and proton beams.
To learn more about helium nuclei, refer to:
brainly.com/question/26226232
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