Calculating Distances In A Storm

Classical Mechanics Level 2

Tim's father has a very large farm that spans several kilometers. During a heavy thunderstorm, he is worried that lightning could have destroyed his barn that is located 1,700 meters from the house. He constantly stares out the window, and feels completely helpless.

If lightning did indeed strike the barn, how long (in seconds) does it take between Tim seeing the lightning strike and hearing the sound of thunder?

Note: Light travels at 300,000,000 m/s, and sound travels at 340 m/s.

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Valteson Santos by Valteson Santos , 27, Brazil

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5 solutions

Discussions for this problem are now closed

Paola Ramírez
Jan 4, 2015

t = d v t=\frac{d}{v}

Time search is t s o u n d − t l i g h t = 1700 340 − 1700 3 × 1 0 9 ≈ 5 s t_{sound}-t_{light}=\frac{1700}{340}-\frac{1700}{3 \times 10^9} \approx 5 s

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Yogesh Ghadge
Apr 11, 2014

t=d/s=1700/340=5

21 Helpful 0 Interesting 0 Brilliant 0 Confused

Moderator note:

Though the value is negligible, you need to mention that you subtract the time taken to travel 1700m.

in the question it is asking for time taken by light and sound then why only we are giving the ans for only sound

kapil arora - 7 years, 1 month ago
Vaibhav Pandey
Apr 13, 2014

t=d/s in case of lightening; time=1700/300000000=0.00000566666 or 0 and in the case of sound;time=1700/340=5 therefore the answer is 5.

7 Helpful 0 Interesting 0 Brilliant 2 Confused

Very good (y)

Valteson da Silva - 6 years, 9 months ago
Liam Clink
Sep 20, 2014

The full solution to this, to be most precise, would be t(sound)-t(light)=1700/340-1700/300000000 Using t=x/v However, the difference caused by the delay for the light is only about 5.7µs, and isn't significant enough to change the answer, so t=1700/340 may be used in this instance. It's not only important to recognize that light takes time to travel, but also how significant that time is.

1 Helpful 0 Interesting 1 Brilliant 0 Confused
Kaif Ahsan
Apr 19, 2014

HIs barn is 1700 m. away from his house. So, the light will reach in 5.67 * 10^-6 s. And sound will reach in 5 seconds. So, the difference will be = 5s.

1 Helpful 0 Interesting 0 Brilliant 1 Confused

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