Select the correct answer.

From a vantage point very close to the track at a stock car race, you hear the sound emitted by a moving car. You detect a frequ

Alexandra [31]

Approximately 15 m/s is the speed of the car.

Explanation:

Given:

speed of sound - 343 m/s

You detect a frequency that is 0.959 times as small as the frequency emitted by the car when it is stationary. So, it can be written as,

$f^{\prime}=0.959 f$

$\frac{f^{\prime}}{f}=0.959$

If there is relative movement between an observer and source, the frequency heard by an observer differs from the actual frequency of the source. This changed frequency is called the apparent frequency. This variation in frequency of sound wave due to motion is called the Doppler shift (Doppler effect). In general,

$f^{\prime}=\left(\frac{v+v_{0}}{v-v_{s}}\right) \times f$

Where,

$f^'$ - Observed frequency

f – Actual frequency

v – Velocity of sound waves

$v_0$ – Velocity of observer

$v_s$ - velocity of source

When source moves away from an observer at rest ( $v_{0} = 0$ ), the equation would be

$f^{\prime}=\left(\frac{v}{v-\left(-v_{s}\right)}\right) \times f$

$f^{\prime}=\left(\frac{v}{v+v_{s}}\right) \times f$

$\frac{f^{\prime}}{f}=\left(\frac{v}{v+v_{s}}\right)$

By substituting the known values, we get

$0.959=\left(\frac{343}{343+v_{s}}\right)$

$0.959\left(343+v_{s}\right)=343$

$0.959(343)+0.959\left(v_{s}\right)=343$

$328.937+0.959 v_{s}=343$

$0.959 v_{s}=343-328.937=14.063$

$v_{s}=\frac{14.063}{0.959}=14.66 \mathrm{m} / \mathrm{s}$

Approximately 15 m/s is the speed of the car.

3 0

3 years ago

Write some interesting facts about isaac newton

Hatshy [7]

Sir Isaac Newton was an English Mathematician,physicist,astronomer,theologian and author who is widely recognized as one of the most influential scientist of all time because of his discovery of gravity(force that attracts a body toward center of earth).

8 0

3 years ago

The main light gathering device of a refractor telescope is

Nataly [62]

It's the "objective" lens ... the big one in the front.

3 0

3 years ago

Atom X contains seven protons and seven neutrons. atom Z contains seven protons and eight neutrons. which of the following state

stiks02 [169]

Answer:

The correct answer is option A: they are isotopes.

Explanation:

From atom X we know that the number of protons is 7 and the number of neutrons is 7 and from atom Z we know that the number of protons is 7 and the number of neutrons is 8.

Since the number of protons of atom X and atom Z is the same, we have that atom X and atom Z is the same element. The difference in the number of neutrons tells us that atom X and atom Z are isotopes. Remember that an isotope is one element that has atoms with different numbers of neutrons.

The mass number is given by:

$A = p + n$

Where n is the number of neutrons and p is the number of protons.

For atom X and atom Z we have:

$A_{x} = 7 + 7 = 14$

$A_{z} = 7 + 8 = 15$

Hence, they have a different mass number.

We know that the element with 7 protons is nitrogen. The first isotope is $^{14}_{7}N$ and the second isotope is $^{15}_{7}N$ . Both isotopes are stables (they are not radioactive).

Therefore, the correct answer is option A: they are isotopes.

I hope it helps you!

3 0

3 years ago

I don’t get this question and i need help!!!

galina1969 [7]

i would say number 2

3 0

3 years ago