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eduard
3 years ago
15

A fire engine is moving south at 35 m/s while blowing its siren at a frequency of 400 Hz.

Physics
1 answer:
vodomira [7]3 years ago
8 0

To solve this problem we will apply the concepts related to the Doppler effect. The Doppler effect is the change in the perceived frequency of any wave movement when the emitter, or focus of waves, and the receiver, or observer, move relative to each other. Mathematically it can be described as

f_d= f_s \frac{(v+v_d)}{(v-v_s)}

Here,

f_d=frequency received by detector

f_s=frequency of wave emitted by source

v_d=velocity of detector

v_s=velocity of source

v=velocity of sound wave

Replacing we have that,

f_d = 400(\frac{(343+18)}{(343-35)})

f_d=422 Hz

Therefore the frequencty that will hear the passengers is 422Hz

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The maximum height a typical person can jump is about 60cm (0.6m). By how much does the gravitational potential energy increase
sasho [114]

The gravitational potential energy will increase by 423.36 J

<h3>How to determine the potential energy at ground level</h3>
  • Mass (m) = 72 kg
  • Acceleration due to gravity (g) = 9.8 m/s²
  • Height (h) = 0 m
  • Potential energy at ground level (PE₁) =?

PE = mgh

PE₁ = 72 × 9.8 × 0

PE₁ = 0 J

<h3>How to determine the potential energy at 60 cm (0.6 m)</h3>
  • Mass (m) = 72 kg
  • Acceleration due to gravity (g) = 9.8 m/s²
  • Height (h) = 0.6 m
  • Potential energy at 60 cm (0.6 m) (PE₂) =?

PE = mgh

PE₂ = 72 × 9.8 × 0.6

PE₂= 423.36 J

<h3>How to determine the change in potential energy </h3>
  • Potential energy at ground level (PE₁) = 0 J
  • Potential energy at 60 cm (0.6 m) (PE₂) = 423.36 J
  • Change in potential energy =?

Change in potential energy = PE₂ - PE₁

Change in potential energy = 423.36 - 0

Change in potential energy = 423.36 J

Learn more about energy:

brainly.com/question/10703928

#SPJ1

8 0
1 year ago
A resistor with R = 300 Ω and an inductor are connected in series across an ac source that has voltage amplitude 500 V . The rat
max2010maxim [7]

Answer:

Explanation:

 Rate of dissipation of energy at resistor

= I² R = 296

current I² = 296/R = 296 / 300

I = 0.9933 A.

Impedence Z = V / I = 500 / .9933

= 503 ohm.

B ) Let it be V

voltage across resistance = 300 x .9933 = 298 v

Now 500² = 298² + V²

V = 401 v

C)  Power factor = R / Z

=300 / 503

= 0.596

6 0
3 years ago
Is a compound considered a pure substance?
IgorLugansk [536]

Answer:

It depends on which compound you use carbon dioxide can be while helium will not but if you where to sum it up it would be use because simply most compounds are considered pure substance.

Explanation:

7 0
2 years ago
Rebecca is learning to play cello and is highly motivated. She is confident that she can learn cello easily and with great abili
Andrej [43]
<span>Rebecca is learning to play cello and is highly motivated. She is confident that she can learn cello easily and with great ability because she already knows how to play violin. From Mischel’s perspective, Rebecca’s attitude is best explained by the expectancies variable. </span>Expectancy<span> is the belief that increased effort will lead to increased performance </span>
6 0
3 years ago
While skateboarding at 19 km/h, Alana throws a tennis ball at 11 km/h to her friend Oliver. If Alana is the reference frame, the
ANTONII [103]

Well, you see, I don't think Alana really is the reference frame. 
Call me paranoid, but I think you changed the reference frame
during the question, and didn't tell us.

In which reference frame is the 19 km/hr measured ?
It CAN'T be Alana's reference frame.  Your own reference
frame moves along with you, and you can't move in it, even
if your name is Alana.

If Alana is the reference frame, and she throws the tennis ball
at 11 km/hr, then the speed of the ball is 11 km/hr in Alana's
reference frame.  Her reference frame moves with  her, so
it makes no difference how fast she is skateboarding in any
other reference frame, who she throws the ball at, or whether
or not he sees it coming and catches it.

Yes, this stuff can get confusing.  And if you think it's bad now,
wait till you start reading some of Prof. Einstein's stuff, where
two people in the same reference frame can watch the same
tennis ball, and not even agree on how fast it's moving, because
THEY're both moving and their own motion makes their rulers
and clocks change !  So they measure different speeds, and
they're both right !

But I got distracted.  I'm sorry.  The point I'm trying to make,
right now when you're just starting to learn reference frames,
is that EVERY time you say a speed, you have to tell which
reference frame the speed is in.  Because, as you're starting
to learn, the same object can have a different speed in every
reference frame.

And, just in case you're thinking about this later today
and you want to ask "Which one is the REAL speed  ?" . . .
THAT's the whole point of learning about reference frames !
There is NO SUCH THING as REAL speed.  It ALWAYS
depends on which reference frame it's measured in.  They're
all different, they're all real, and they're all correct.

5 0
3 years ago
Read 2 more answers
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