Yet Another Cycling Forum

General Category => The Knowledge => OT Knowledge => Topic started by: Martin on 17 October, 2017, 09:28:26 pm

Title: car conundrum
Post by: Martin on 17 October, 2017, 09:28:26 pm
This has had a few cow orkers scratching their heads

a car drives a mile at 30mph; it then drives another mile.

How fast must it drive the second mile to average 60mph for 2 miles?
Title: Re: car conundrum
Post by: Von Broad on 17 October, 2017, 09:34:29 pm
Well it's obviously not the obvious, but I'll say it anyway just to get it out of the way - 90mph
[crap at these kind of things]
Title: Re: car conundrum
Post by: Feanor on 17 October, 2017, 09:35:19 pm
Quote from: Martin on 17 October, 2017, 09:28:26 pm
This has had a few cow orkers scratching their heads

a car drives a mile at 30mph; it then drives another mile.

How fast must it drive the second mile to average 60mph for 2 miles?

To average 60mph for 2 miles, you must complete the 2 miles in 2/60 = 0.033333 hours.
If you have already driven 1 mile at 30 mph, you have already used 1/30 = 0.033333 hours.

You are already out of time.
You have no remaining time.
You would need to drive infinitely fast for the remaining mile.
You are DNF.
Title: Re: car conundrum
Post by: Diver300 on 17 October, 2017, 09:35:55 pm
R17

In excess of c.

(click to show/hide)
Title: Re: car conundrum
Post by: Martin on 17 October, 2017, 09:37:23 pm
Quote from: Feanor on 17 October, 2017, 09:35:19 pm
Quote from: Martin on 17 October, 2017, 09:28:26 pm
This has had a few cow orkers scratching their heads

a car drives a mile at 30mph; it then drives another mile.

How fast must it drive the second mile to average 60mph for 2 miles?

To average 60mph for 2 miles, you must complete the 2 miles in 2/60 = 0.033333 hours.
If you have already driven 1 mile at 30 mph, you have already used 1/30 = 0.033333 hours.

You are already out of time.
You have no remaining time.
You are DNF.

correct!
Title: Re: car conundrum
Post by: sojournermike on 17 October, 2017, 09:38:56 pm
Quote from: Diver300 on 17 October, 2017, 09:35:55 pm
R17

In excess of c.

(click to show/hide)

Depending on the observer you could make a case for c, relying on time dilation to allow you to travel the second mile in zero perceived time. In practice the acceleration would probably crush you...


Of course, someone will now point out that it's not possible to accelerate up to c due to general relativistic effects.


I'll get me coat
Title: Re: car conundrum
Post by: Martin on 17 October, 2017, 09:39:35 pm
another one;

a man is pushing his car when he suddenly stops outside a hotel; suddenly he feels very disappointed

why?
Title: Re: car conundrum
Post by: Diver300 on 17 October, 2017, 09:39:51 pm
Quote from: Von Broad on 17 October, 2017, 09:34:29 pm
Well it's obviously not the obvious, but I'll say it anyway just to get it out of the way - 90mph
[crap at these kind of things]
That would have been the correct answer if the question had had the car driving at 30 mph for one minute. If it then drove at 90 mph for a second minute it would have averaged 60 mph for the two minutes.
Title: Re: car conundrum
Post by: Diver300 on 17 October, 2017, 09:40:34 pm
Quote from: Martin on 17 October, 2017, 09:39:35 pm
another one;

a man is pushing his car when he suddenly stops outside a hotel; suddenly he feels very disappointed

why?
Monopoly
Title: Re: car conundrum
Post by: Pingu on 17 October, 2017, 09:51:33 pm
Was it one of those Google cars (https://yacf.co.uk/forum/index.php?topic=82822.0)?
Title: Re: car conundrum
Post by: hellymedic on 17 October, 2017, 09:52:22 pm
Quote from: Diver300 on 17 October, 2017, 09:40:34 pm
Quote from: Martin on 17 October, 2017, 09:39:35 pm
another one;

a man is pushing his car when he suddenly stops outside a hotel; suddenly he feels very disappointed

why?
Monopoly

And the hotel belongs to AN Other, who shouts RENT!
Title: Re: car conundrum
Post by: hatler on 17 October, 2017, 10:01:31 pm
If it takes 5 minutes for 5 machines to make 5 widgets, how long does it take a 100 machines to make a 100 widgets ?
Title: Re: car conundrum
Post by: Hot Flatus on 17 October, 2017, 10:10:14 pm
5 minutes
Title: Re: car conundrum
Post by: Martin on 17 October, 2017, 10:53:20 pm
not car related but make one 7 letter  one 5 letter one 4 letter and three 3 letter words (horizontal or vertical) using these letters only once each to fill in the gaps (it's supposed to be a pyramid)

Y Y R R E E A P U T H P

       P
    B - -
  T - - - -
 T - - - - - -
Title: Re: car conundrum
Post by: Martin on 17 October, 2017, 11:05:04 pm
an equilateral triangle a square and a circle all have the same area; which has the longest circumference?
Title: Re: car conundrum
Post by: Jaded on 17 October, 2017, 11:15:47 pm
The Volvo  ???
Title: Re: car conundrum
Post by: mrcharly-YHT on 18 October, 2017, 08:03:31 am
Quote from: Martin on 17 October, 2017, 11:05:04 pm
an equilateral triangle a square and a circle all have the same area; which has the longest circumference?
Gut feeling, without checking formulae, says the triangle. Circle has the least.
Title: Re: car conundrum
Post by: LittleWheelsandBig on 18 October, 2017, 08:22:39 am
MrC is correct
Title: Re: car conundrum
Post by: Mr Larrington on 18 October, 2017, 08:46:22 am
If it takes a man and a half a day and a half to dig a hole and a half, how long does it take a fly with clogs on to walk through a barrel of treacle?

Show your working.
Title: Re: car conundrum
Post by: Ben T on 18 October, 2017, 01:26:07 pm
Quote from: Martin on 17 October, 2017, 11:05:04 pm
an equilateral triangle a square and a circle all have the same area; which has the longest circumference?
a triangle and a square don't have "circumference", they have perimeter.
Title: Re: car conundrum
Post by: hellymedic on 18 October, 2017, 02:02:48 pm
Quote from: Ben T on 18 October, 2017, 01:26:07 pm
Quote from: Martin on 17 October, 2017, 11:05:04 pm
an equilateral triangle a square and a circle all have the same area; which has the longest circumference?
a triangle and a square don't have "circumference", they have perimeter.

Indeed but pedants' threads are elsewhere.

Circles have the smallest perimeter for a given area and spheres the smallest surface area for a given volume.

Red blood cells are usually biconcave discs to increase surface area.
Spherocytosis (spherical red blood cells) is a known medical problem.
Title: Re: car conundrum
Post by: Martin on 18 October, 2017, 03:01:23 pm
Quote from: hellymedic on 18 October, 2017, 02:02:48 pm
Red blood cells are usually biconcave discs to increase surface area.

possibly more to do with the ability to deform in small blood capillaries