C4 Math Problem
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Joined: Sep 2004
Posts: 92
Likes: 0
From: Columbia Missouri
Originally Posted by JCD
299,792,458 meters per second would do it thanks to relativity (time would stand still for the observer).
Or is that only for a straight line?
Or is that only for a straight line?
Melting Slicks
Joined: Dec 2004
Posts: 2,943
Likes: 14
From: Gurley (Keel Mtn, Sweet Home) Alabama
"A driver runs 30 MPH for his first lap (in his MG I guess). How fast does he have to go for the second lap to bring his average up to 60 MPH for the two laps?
Actually, he can't do it. If it's a 1 mile track, it took him 2 minutes to go around it at 30 MPH. To average 60 for both laps he would have to take 2 minutes total. He's out of time! Sorry, kind of a trick question."
Actually, I think 90mph is the correct answer. The way you worded the question only indicated that he drove one lap at 30mph, and wondered how fast he'd have to drive the second lap to average 60mph for the two laps. You didn't mention anything about time...???? Or I am completely fooled!
Actually, he can't do it. If it's a 1 mile track, it took him 2 minutes to go around it at 30 MPH. To average 60 for both laps he would have to take 2 minutes total. He's out of time! Sorry, kind of a trick question."
Actually, I think 90mph is the correct answer. The way you worded the question only indicated that he drove one lap at 30mph, and wondered how fast he'd have to drive the second lap to average 60mph for the two laps. You didn't mention anything about time...???? Or I am completely fooled!
Melting Slicks
Joined: May 2004
Posts: 2,286
Likes: 2
From: Stamping Ground KY
Originally Posted by MyOtherCar
Or I am completely fooled!
V2 = V1 * Va / (2 * V1 - Va)
[where V1 = first lap speed, V2 = 2nd lap speed, Va = average velocity)
So if the average velocity is equal to double V1 you'll get a zero in the denominator (that's maths way of saying it can't be done).
The catch is that you can't say (V1+V2)/2=Va because you spend less time at V2. Va is actually:
Va= 2*V1*V2/(V1+V2)
In closing I'd like to add: Math sux r0x5
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Joined: Sep 2004
Posts: 92
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From: Columbia Missouri
Originally Posted by MyOtherCar
"A driver runs 30 MPH for his first lap (in his MG I guess). How fast does he have to go for the second lap to bring his average up to 60 MPH for the two laps?
Actually, he can't do it. If it's a 1 mile track, it took him 2 minutes to go around it at 30 MPH. To average 60 for both laps he would have to take 2 minutes total. He's out of time! Sorry, kind of a trick question."
Actually, I think 90mph is the correct answer. The way you worded the question only indicated that he drove one lap at 30mph, and wondered how fast he'd have to drive the second lap to average 60mph for the two laps. You didn't mention anything about time...???? Or I am completely fooled!
Actually, he can't do it. If it's a 1 mile track, it took him 2 minutes to go around it at 30 MPH. To average 60 for both laps he would have to take 2 minutes total. He's out of time! Sorry, kind of a trick question."
Actually, I think 90mph is the correct answer. The way you worded the question only indicated that he drove one lap at 30mph, and wondered how fast he'd have to drive the second lap to average 60mph for the two laps. You didn't mention anything about time...???? Or I am completely fooled!
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Burning Brakes
Joined: Oct 2003
Posts: 818
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From: Portland OR
Here's another fun one I use with my physics students to get them understand what I mean by eloquence. Two bicycles 20 miles apart are traveling at 10 mph toward each other. There is a fly that starts on the wheel of one bike and flys at 15 mph toward the other bike. It then touchs the other tire, instantaneously turns around and flys back to the first bike. How far does the fly fly before the fly don't fly no more?
This can be hard or it can be very easy.
This can be hard or it can be very easy.
Advanced
Joined: Sep 2004
Posts: 92
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From: Columbia Missouri
Originally Posted by quantum-theory
Here's another fun one I use with my physics students to get them understand what I mean by eloquence. Two bicycles 20 miles apart are traveling at 10 mph toward each other. There is a fly that starts on the wheel of one bike and flys at 15 mph toward the other bike. It then touchs the other tire, instantaneously turns around and flys back to the first bike. How far does the fly fly before the fly don't fly no more?
This can be hard or it can be very easy.
This can be hard or it can be very easy.
Team Owner
Joined: Apr 2004
Posts: 36,040
Likes: 4
From: All great change begins at the dinner table Ronald Reagan
Originally Posted by quantum-theory
Here's another fun one I use with my physics students to get them understand what I mean by eloquence. Two bicycles 20 miles apart are traveling at 10 mph toward each other. There is a fly that starts on the wheel of one bike and flys at 15 mph toward the other bike. It then touchs the other tire, instantaneously turns around and flys back to the first bike. How far does the fly fly before the fly don't fly no more?
This can be hard or it can be very easy.
This can be hard or it can be very easy.
This is easy, the fly was run over, it doesn't fly no more.
Melting Slicks
Joined: Jul 2003
Posts: 2,140
Likes: 0
From: Cincinnati Ohio
Wow you guys put some numbers up 
I always looked at it like this.....
60 is a mile a minute
4 minutes=4 miles
At 80 Im getting an extra mile for every 4 minutes of driving
It doesnt seem like much but......
Its about 380 miles to Grandmas house (in Youngstown)
I got from Youngstown Ohio back to Cincy last Thanksgiving in less than 4 and a half hours
Gotta love it
I always looked at it like this.....
60 is a mile a minute
4 minutes=4 miles
At 80 Im getting an extra mile for every 4 minutes of driving
It doesnt seem like much but......
Its about 380 miles to Grandmas house (in Youngstown)
I got from Youngstown Ohio back to Cincy last Thanksgiving in less than 4 and a half hours
Gotta love it
Safety Car
Joined: Dec 2004
Posts: 4,088
Likes: 0
From: Poop land
The simplest way to put it is: 3600 divided by your time in seconds. So if you were traveling Mach 5, (3600 mph) you could do a mile in 1 second. If I can speed skate 1 mile in 4 minutes (240 seconds) then my average speed would be 15 mph. Same way goes that If you drive 240 mph, you could do a 15 second mile! This is a proven method that that the Olympics use to calculate average speeds. I'm afraid I love math too much.
