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3 years ago

Explain why a fire engine’s siren sounds lower in pitch after the fire engine passes you.

2 answers:

5 0

When a sound source is moving toward you, you hear a higher frequency than the source is putting out, and when the source is moving away from you, you hear a lower frequency than the real one. The whole process is called the Doppler effect. It works with light too.

Sedbober [7]3 years ago

3 0

Explanation:

Doppler effect: It is the phenomenon which occurs when there is relative motion between listener and source.

In this phenomenon, there is an apparent change in the frequency. There is an increase or decrease in frequency.

The frequency gets lower when the source and the listener are moving away from each other.

The frequency gets higher when the source and the listener are moving towards each other.

The pitch depends on the frequency. When the frequency increases then the pitch of the sound gets louder. When the frequency decreases then the pitch of the sound gets lower.

In the given problem, a fire engine's siren sounds lowers in pitch after the fire engine passes. Here, the source and the listener are moving away from each other. The frequency gets lower. Then, the pitch of the sound will also get lower.

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A projectile fired up into the air at an angle has a range of 235 m and a flight time of 47 s.

madam [21]

<h2>Answer:5 $ms^{-1}$ ,133.6 $m$ ,51.18 $ms^{-1}$ </h2>

Explanation:

Let $v_{x}$ , $v_{y}$ be the horizontal and vertical components of velocity.

Question a:

Horizontal component of velocity is the ratio of range and time of flight.

So,horizontal component of velocity is $\frac{235}{47}=5ms^{-1}$

So, $v_{x}=5ms^{-1}$

Question b:

Time of flight= $\frac{2v_{y}}{g}$

So, $v_{y}=\frac{47\times 9.8}{2}=51.18ms^{-1}$

Maximum height is given by $\frac{v_{y}^{2}}{2g}$

So,maximum height is $\frac{51.18^{2}}{2\times 9.8}=133.6m$

Question c:

The vertical velocity is already calculated in Question b.

$v_{y}=51.18ms^{-1}$

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photoshop1234 [79]

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jek_recluse [69]

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mina [271]

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Explanation:

Solids

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Liquids

These have a an internal molecular structure with comparatively more spaces with one another. Liquids have a property to flow and change shape according to the container it is taken.

Gases

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A complete ionized gas which has equal amount of positively and negatively charged ions. The best example of plasma is a plasma-ball.

Phase transformation among the four forms of matter

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A matter changing from a solid phase to liquid phase is known as melting. Ex: Ice into water

Freezing

A matter changing from liquid to solid is known as freezing.

Boiling

When the liquid is heated to its boiling point, this gets transformed into the state of gas where liquid's pressure equals to the external pressure.

Evaporation

Once the liquid reached the temperature range above the boiling point ad starts converting into vapours or gaseous state.

Condensation

When the gases changes from the gaseous phase to liquid phase, this is called condensation.

Sublimation

The change of solid into gas is called as sublimation.

Deposition

Deposition refers the thermodynamic process where phase transition takes place as the gas solidifies without passing through the liquid phase. An example: the process of converting water vapour from frozen air directly into ice without initially becoming a liquid.

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