A classical mechanics problem by Tunk-Fey Ariawan

Classical Mechanics Level 1

It is noontime and the sun is shinning overhead. If the sun suddenly stopped shining, how long in seconds would it take you to become aware of the fact?

Details and assumptions :

Distance between the Sun and the Earth $= 1\text{ AU}=1.5\times 10^{8}\text{ km}$
The speed of light $=3\times 10^{8}\text{ m/s}$
$1$ day on the earth $=86,400\text{ s}$

Credit image : Wikipedia

2 0.5 172.8 500

5 solutions

Tunk-Fey Ariawan
Mar 25, 2014

The time taken $(t)$ for people on earth become aware of the fact is $\begin{aligned} t&=\frac{\text{Distance between the Sun and the Earth}}{\text{The speed of light}}\\ &=\frac{1.5\times10^{11}\text{ m}}{3\times10^{8}\text{ m/s}}\\ &=\boxed{\color{#3D99F6}{500\text{ s}}} \end{aligned}$

$\text{\# }\mathbb{Q.E.D.}\text{ \#}$

I read this in a book a while back, but I remembered it being about 8 seconds and not minutes. Luckily it was multiple choice.😄

Robert Fritz - 7 years, 2 months ago

Very good Robert! :)

Anyway, did you know my point decreased almost $50$ points when I incorrectly answered problem Measuring the diameter of the moon . It took hours for me to get back to level $5$ . Jeez! The system must have been error.

UPDATE : Brilliant already fix the system and give me back my lost point.

Tunk-Fey Ariawan - 7 years, 2 months ago

I avoid all the low rated problems...having solved them i just move on, hence avoiding any risk

Shikhar Jaiswal - 7 years, 2 months ago

That stinks. I lost some points on that question too. I knew the right answer, but when scrolled down I acidently pressed on the wrong one.

Robert Fritz - 7 years, 2 months ago

@Robert Fritz – :D Same feeling,bro.I've lost tons of points having done that,but not for this one.

Shantanu Nathan - 7 years, 2 months ago

I think you probably shouldn't post the answer to the question that you missed. :D

Finn Hulse - 7 years, 2 months ago

@Finn Hulse – Sorry Fine. That's really stupid of me. I've edited my comment. Thanks for noticing me. Anyway, I lost again lots points when answer Snehal problem. I should listen Shikhar advice, avoid the low rated problems especially multiple choices. :(

Tunk-Fey Ariawan - 7 years, 2 months ago

@Tunk-Fey Ariawan – Yeah... Something that I really hate is that because I have really low levels, Brilliant feeds me problems that are on my "level". Those problems are the ones that if you miss, you lose 100 points, and that if you get right, you gain 5 points. Really annoying.

Finn Hulse - 7 years, 2 months ago

@Finn Hulse – Yeah!? That's really annoying me too. Anyway, I've just followed you & Robert. Nice to know you guys... :)

Tunk-Fey Ariawan - 7 years, 2 months ago

@Tunk-Fey Ariawan – Thanks! I feel honored.

Robert Fritz - 7 years, 2 months ago

@Tunk-Fey Ariawan – Hey yeah, nice talking with you. Have you tried any of my problems?

Finn Hulse - 7 years, 2 months ago

@Finn Hulse – Recently, I've answered your problem: "be smart about this one".

Tunk-Fey Ariawan - 7 years, 2 months ago

it takes 8 minutes not 8 seconds

Prajwal Kavad - 7 years, 2 months ago

It's about 8 minutes, possibly a source of confusion.

Michael Reilly - 6 years, 3 months ago

haha.. tumben ngepost soal yang bisa ku jawab.

Hafizh Ahsan Permana - 7 years, 2 months ago

light takes a time of 8 minutes and 20 seconds in reaching earth.Obviously it will take same time when people come to know about darkness.

Inzamam Ali Khawaja - 7 years, 2 months ago

i have done it

Shivangi Gupta - 7 years, 1 month ago

Faiz Hassan
Mar 28, 2014

I WAS ABLE TO SOLVE IT CAUSE ONCE I ASKED MY TEACHER THE DISTANCE BETWEEN SUN AND EARTH SHE DIDN'T TELL ME SO MADE MY OWN METHOD TO FIND IT :)

why they gave us the duration for an rotation of earth?

Sittra Damon - 7 years, 2 months ago

its near about 8min 18sec

Ashish Chaurasiya - 7 years, 1 month ago

Arc Wolf
Nov 2, 2015

The sun is around 8 light minutes from the earth.

Multiplying its distance away in light minutes by 60 gets you the sun's distance in light seconds.

The last photon from the sun would hit at 500 light seconds.

Keanu duPont
Dec 28, 2014

the earth is 149,600,000,000 m away from the sun. light travels at 299,792,458 meters/second. so would cover the distance in 499.0118864164355 sec

Prajwal Kavad
Apr 6, 2014

light takes a time of 8 minutes and 20 seconds in reaching earth.Obviously it will take same time when people come to know about darkness.

A classical mechanics problem by Tunk-Fey Ariawan

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