- 13 Aug '06 01:22So our intrepid hero is in a race and its 1000 Km. He averages only 50 Km/hr in the first 500 Km and he realizes he needs to average 100 Km.hr in the second half to win. So ignoring the acceleration time, how fast does he have to go in the second half to average 100KM/hr?

Xanthos, I did it in my head so I know you can too, so let someone else have a go, ok? I hope you realize that's a compliment. - 13 Aug '06 02:09 / 1 edit

How fast does he have to go in the second half to average 100 Km/hr for the whole race. Its the stupid one.*Originally posted by XanthosNZ***Does he need to average 100km/hr for the second half or does he need to average 100km/hr for the entire race to win?**

Your question says the first, but that's a stupid problem. If it's the second then you should know that this has been posted multiple times previously.

Lets just see who gets it! - 13 Aug '06 02:55

"he realizes he needs to average 100 Km.hr in the second half to win."*Originally posted by sonhouse***How fast does he have to go in the second half to average 100 Km/hr for the whole race. Its the stupid one.**

Lets just see who gets it!

So he has to average 100km/hr in the second half which he can do by averaging 100km/hr in the second half. - 13 Aug '06 04:20

Oooh, that was tricky. I was about to post the wrong answer, but after going through it again, the answer is: The speed of light. ( or "impossible to do"*Originally posted by sonhouse***So our intrepid hero is in a race and its 1000 Km. He averages only 50 Km/hr in the first 500 Km and he realizes he needs to average 100 Km.hr in the second half to win. So ignoring the acceleration time, how fast does he have to go in the second half to average 100KM/hr?**

Xanthos, I did it in my head so I know you can too, so let someone else have a go, ok? I hope you realize that's a compliment.

Using the formula d(distance)=v(velocity)/t(time). Substitutuing numbers in, we get t= 10 hours in order for him to finish with average speed being 100KM per hour. However, if you go through it, you realize that it takes 10 sec to go through the first half alone-- leaving zero time for the second half. - 13 Aug '06 04:59

You got it! Imfrappingpossible! You need to have more than C even, like infinite!*Originally posted by abejnood***Oooh, that was tricky. I was about to post the wrong answer, but after going through it again, the answer is: The speed of light. ( or "impossible to do"**

Using the formula d(distance)=v(velocity)/t(time). Substitutuing numbers in, we get t= 10 hours in order for him to finish with average speed being 100KM per hour. However, if you go through it, you re ...[text shortened]... at it takes 10 sec to go through the first half alone-- leaving zero time for the second half. - 13 Aug '06 04:59

Assume he travels at c for the remaining 500km of the race. Then he would have taken 10 hours and 0.000167 seconds to finish the race.*Originally posted by abejnood***Oooh, that was tricky. I was about to post the wrong answer, but after going through it again, the answer is: The speed of light. ( or "impossible to do"**

Using the formula d(distance)=v(velocity)/t(time). Substitutuing numbers in, we get t= 10 hours in order for him to finish with average speed being 100KM per hour. However, if you go through it, you re ...[text shortened]... at it takes 10 sec to go through the first half alone-- leaving zero time for the second half.

That would give an average speed of 27.778 m/s which is 99.99999954 km/hr. That sthill wouldn't be enough.

Of course here we are applying Newtonian physics to the speed of light which is of course inaccurate.

PS. When doing Physics problems be careful with your units. hours and seconds are definitely not the same thing. - 13 Aug '06 05:10 / 1 edit

Well I guess it wasn't THAT stupid, eh!*Originally posted by XanthosNZ***Assume he travels at c for the remaining 500km of the race. Then he would have taken 10 hours and 0.000167 seconds to finish the race.**

That would give an average speed of 27.778 m/s which is 99.99999954 km/hr. That sthill wouldn't be enough.

Of course here we are applying Newtonian physics to the speed of light which is of course inaccurate.

PS. W ...[text shortened]... ysics problems be careful with your units. hours and seconds are definitely not the same thing.

Looking at the original posting, it could have been better worded.

It helps to go over these things afterwards it appears. - 13 Aug '06 05:11 / 1 edit

You still don't get it do you? Your question was phrased in such a way that the question asked was "What speed does he have to travel in the second half of the race to average 100km/hr*Originally posted by sonhouse***Well I guess it wasn't THAT stupid, eh!****in the second half of the race.**

Clearly the answer to that question is 100km/hr. That is the interpretation that is stupid. The other interpretation (the one you intended and the only abe answered) is not stupid merely repetitive. - 13 Aug '06 05:29

Thats what I meant when I re-read it, it was worded wrong. I did not know this kind of problem had been posted here before, show me the link if you will.*Originally posted by XanthosNZ***You still don't get it do you? Your question was phrased in such a way that the question asked was "What speed does he have to travel in the second half of the race to average 100km/hr [b]in the second half of the race.**

Clearly the answer to that question is 100km/hr. That is the interpretation that is stupid. The other interpretation (the one you intended and the only abe answered) is not stupid merely repetitive.[/b]