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Alja [10]
3 years ago
14

Your foot is trapped under a railway sleeper. You feel the rail vibrate and then 20s later hear a faint whistle. Estimate how mu

ch time you have to free yourself. You may assume the railway way is a straight line and: Velocity of sound in air = 0.33 km/s , The velocity of vibration along the track = 5 km/s,
Train speed: 60 km/hr, 100 km/hr and 150 km/hr
Physics
1 answer:
lions [1.4K]3 years ago
7 0

Explanation:

Speed of sound in air = 0.33 km/s

Speed of vibration along the track = 5 km/s

Time = Distance / Speed

\frac{s}{0.33}-\frac{s}{5}=20\\\Rightarrow \frac{467}{165}s=20\\\Rightarrow s=20\times \frac{165}{467}\\\Rightarrow s=7.06638\ km

When train speed: 60 km/hr

Time=\frac{7.06638}{\frac{60}{3600}}=423.9828\ s

Time you will have is 423.9828 s

When train speed: 100 km/hr

Time=\frac{7.06638}{\frac{100}{3600}}=254.38968\ s

Time you will have is 254.38968 s

When train speed: 150 km/hr

Time=\frac{7.06638}{\frac{150}{3600}}=169.59312\ s

Time you will have is 169.59312 s

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Ghella [55]

We can define average speed as the quotient between the whole distance traveled and the time it takes to travel that distance, and the velocity as the quotient between the displacement and the time it takes to displace that quantity.

We will find that:

Average speed =  2.6×10^2 km/day

Velocity = 2.52×10^2 km/day

So we know that:

The tent travels:

1.70×10^4 km to the south

6.00×10^2 km to the north

1.44×10^4 km to the south.

The total distance traveled is just the sum of the 3 above distances:

total distance = 1.70×10^4 km +  6.00×10^2 km + 1.44×10^4 km

Notice that the second term has a different exponent than the others, so to have the same exponent we can write:

6.00×10^2 km = 0.06×10^4 km

Now we get:

total distance = 1.70×10^4 km + 0.06×10^4 km + 1.44×10^4 km

total distance = (1.70 + 0.06 + 1.44)×10^4 km

<u>total distance = 3.2×10^4 km</u>

And it travels that distance in 122 days, then the average speed is:

AS = (3.2×10^4 km)/(122 days) = 2.6×10^2 km/day

Now we need to find the displacement, which is the difference between the final position and the initial position, the displacement will just be:

d =  1.70×10^4 km - 0.06×10^4 km + 1.44×10^4 km

(We add the distance traveled to south and subtract the distance that it travels due north)

d = (1.70 - 0.06 + 1.44)×10^4 km = 3.08×10^4 km

Then the velocity will be:

v = (3.08×10^4 km)/(122 days) = 2.52×10^2 km/day

Because we defined south as positive and north as negative, having a positive velocity means that the direction of the <u>velocity is due south.</u>

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3 0
3 years ago
In which situation is maximum work considered to be done by a force?
umka2103 [35]

Answer:

A) When the angle between the Force (F) and Displacement (x) is 0°, because, Work done (W) is directly proportional to the Cosine of the Angle between the Force applied and the resultant displacement of the subject.

W = F•x cos ∅

If ∅ = 0°,

W = F•x ===> Maximum Work Done.

If ∅ = 45°,

W = F•x/√2

If ∅ = 90°,

W = 0

If ∅ = 180°,

W = –F•x ===> Minimum Work Done.

7 0
3 years ago
The sound intensity at a distance 2.00 m from a sound source is 5.00 Find the total sound energy emitted by the source in each s
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Answer:

     P = 251, 3 W

Explanation:

The intensity is defined as the power emitted per unit area

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Since sound is distributed in all directions spherical shape, the area of ​​a sphere is

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let's calculate

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No. The correct answer is A.

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