# Another kinematics puzzle..

#### triggernum5

Joined May 4, 2008
216
If this seems too easy, then just let it slide a while..
If you were to ride a bike around a quarter-mile track once at an average speed of 10mph, what must your average speed be during a second lap, to make your average speed over both laps equal to 20mph?

#### Mark44

Joined Nov 26, 2007
628
Triggernum5, check your PM for my answer. I don't want to give it away too soon.
Mark

#### silvrstring

Joined Mar 27, 2008
159
Cool, thanks.

#### thingmaker3

Joined May 16, 2005
5,084
I was watching Stargate SG-1 DVDs last night. According to the plot lines, there were two of the worm-hole machines on Earth.

#### triggernum5

Joined May 4, 2008
216
Actually, I don't think a stargate would do it, they said its cold few seconds en route once in the show.. And even if it did, it would be tough to say you did anything since the point of origin would also be the point of destination..

#### Voltboy

Joined Jan 10, 2007
197
20=$$\frac{10+x}{2}$$
= (20*2)-10 = 30mph??

#### triggernum5

Joined May 4, 2008
216
How long would that take?

#### recca02

Joined Apr 2, 2007
1,214
If you travel half the distance with half the speed, can you still reach in time?

#### triggernum5

Joined May 4, 2008
216
I dunno.. Perhaps if one knew a bit about tachyons.. So is anybody still stumped by this, or what?

#### Ratch

Joined Mar 20, 2007
1,070
Voltboy,

20=
= (20*2)-10 = 30mph??
OK, Vboy, I am questioning your answer. It takes 1/40 of an hour to travel the first quarter mile. It takes 1/120 of an hour to travel the next quarter mile at 30 mph. That makes the total time of 1/30 of an hour. Dividing that time into the total distance of 1/2 mile gives a average speed of 50 mph. Was that a discovery?

triggernum5,

I believe everyone appreciates the impossible solution.

Ratch