Nijholts Nuts
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« on: Sunday, June 6, 2010, 16:20:02 » |
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...solve this little conundrum I've just encoutered whilst revising...
A River, 20m wide and 4m deep drains a field that is 3000km square in which the average rain fall is
48cm/Metre Square/Year. One quarter of the rainfall returns to the atmosphere via evaporation but the remainder drains into the river. What is the average speed of the river current?
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Processed Beats
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« Reply #1 on: Sunday, June 6, 2010, 16:21:33 » |
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Speed = distance/time
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Phil_S
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« Reply #2 on: Sunday, June 6, 2010, 16:25:21 » |
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You sure the field is 3,000 square Kilometres !
It's a bloody big field !
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BrightonRed
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« Reply #3 on: Sunday, June 6, 2010, 16:43:37 » |
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Not sure if this will end anywhere but..
3,000km^2 = 3,000,000,000m^2
48cm = 0.48m
Volume of water that falls annually = 0.48 x 3,000,000,000 = 1,440,000,000m^3
Only 25% exits via the river = 0.25 x 1,440,000,000 = 360,000,000m^3 per year.
So we've got a volume and a period. Just need to think about the rest.
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Nijholts Nuts
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« Reply #4 on: Sunday, June 6, 2010, 16:45:27 » |
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3/4 exits via the river 1/4 evaporates
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jonny72
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« Reply #5 on: Sunday, June 6, 2010, 16:48:50 » |
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You sure the field is 3,000 square Kilometres !
It's a bloody big field !
Just a little bit smaller than Wiltshire in fact. |
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rich
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« Reply #6 on: Sunday, June 6, 2010, 16:53:50 » |
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i dont think this can be done from that info. what level is it? ie gcse, A / AS level?
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BrightonRed
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« Reply #7 on: Sunday, June 6, 2010, 16:55:24 » |
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ok, 0.75 x 1,440,000,000 = 1,080,000,000m^3 per year
1 year = 31,536,000 seconds
1,080,000,000 / 31,536,000 = 34.25m^3/sec
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ron dodgers
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« Reply #8 on: Sunday, June 6, 2010, 16:56:51 » |
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just under 1 mile an hour
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Barry Scott
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« Reply #9 on: Sunday, June 6, 2010, 17:01:59 » |
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I make it 1.54 mph. The river's current that is.  |
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BrightonRed
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« Reply #10 on: Sunday, June 6, 2010, 17:04:05 » |
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Average Velocity = Flow Rate / Cross Sectional Area
= 34.25m^3/sec / 80m^2
0.428m/s
or 0.96 mph
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Nijholts Nuts
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« Reply #11 on: Sunday, June 6, 2010, 17:08:53 » |
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Its Degree level Engineering, and I believe I owe Brighton Red a pint...well done.
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leefer
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« Reply #12 on: Sunday, June 6, 2010, 17:15:08 » |
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Average Velocity = Flow Rate / Cross Sectional Area
= 34.25m^3/sec / 80m^2
0.428m/s
or 0.96 mph
Einstein or what well done BR.....silly question as usual but dosn,t the strength of the wind have any bearing on the flow of a river? |
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ron dodgers
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shaddap your face
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« Reply #13 on: Sunday, June 6, 2010, 17:54:46 » |
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Average Velocity = Flow Rate / Cross Sectional Area
= 34.25m^3/sec / 80m^2
0.428m/s
or 0.96 mph
yes - I agree - that's what I said |
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Mexicano Rojo
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« Reply #14 on: Sunday, June 6, 2010, 18:26:23 » |
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bloody hell mr red, you seem like a right thick bumpkin cunt when i have ever been in your company  |
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