A river 90 m wide and 2.5 m deep flows at 1.4 m/s.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A river wide and deep flows at . Downstream it is wide and deep. How fast does it flow there?
Need a reminder? The key ideaShow
Continuity: for steady flow of a liquid, ; the volume flow rate is the same through every section. The area goes as the diameter squared.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Areas. and .
Step 2. Speed. .
Answer: .
Check. The river is half as wide but deeper, so it speeds up by less than twice.
Watch out. Use the whole cross-section, not the width alone.
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