# Another kinematics puzzle..

Discussion in 'Physics' started by triggernum5, Aug 2, 2008.

1. ### triggernum5 Thread Starter Senior Member

May 4, 2008
216
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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?

2. ### Mark44 Well-Known Member

Nov 26, 2007
626
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Triggernum5, check your PM for my answer. I don't want to give it away too soon.
Mark

3. ### silvrstring Active Member

Mar 27, 2008
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Cool, thanks.

4. ### thingmaker3 Retired Moderator

May 16, 2005
5,072
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I was watching Stargate SG-1 DVDs last night. According to the plot lines, there were two of the worm-hole machines on Earth.

5. ### triggernum5 Thread Starter Senior Member

May 4, 2008
216
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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..

6. ### Voltboy Active Member

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

7. ### triggernum5 Thread Starter Senior Member

May 4, 2008
216
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How long would that take?

8. ### recca02 Senior Member

Apr 2, 2007
1,211
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If you travel half the distance with half the speed, can you still reach in time?

9. ### triggernum5 Thread Starter Senior Member

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

10. ### Ratch New Member

Mar 20, 2007
1,068
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Voltboy,

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