How a Lock Works


Lock cycle simulation

Mathise Pic
Did you know that all locks on the Welland Canal are filled and emptied by gravity? No pumps are used, water just flows from a higher level to a lower one.



Geo Pic
Yes I did. Suppose a ship is sailing from Lake Ontario to Lake Erie. Then it has to be raised through each lock to a higher water level. First the ship enters the lock and is secured with ropes or cables to bollards - those mushroom looking things. Next, the gates are closed and large valves are opened to allow water from the canal above the lock to flow through large pipes. The ship begins to rise. When the water level has risen to that in the canal above the lock, the gates are opened and the ship sails out.



Mathise Pic
I thought it would be more complicated than that.



Geo Pic
I heard that it takes approximately ten minutes for the lock to fill up or empty. We can use this information to determine the rate at which a lock empties or fills up.



Mathise Pic
OK. The rate is the volume of water required to fill the lock divided by how long it takes to empty or fill. I read somewhere that you need about 90 000 cubic metres of water to raise a ship in the lock.




Given the information from Mathise and Geo, Calculate the rate of flow of water into or out of the lock in metres per second.

Rate of Flow Solution



Geo Pic
It it fast or slow ?





Mathise Pic
Fast or Slow compared to what ?



Geo Pic
How about the number of bathtubs per second!




Trig Pic
Great Idea. Assume that a bathtub holds 0.035 cubic metres of water.







Using Geo's suggestion, Trig's information and your solution to the rate of flow problem above, calculate the rate of flow into or out of the lock in bathtubs per second.

See Bathtub Solution



Mathise Pic
Holy smoke! Now I know why they don't want anyone swimming around the locks. You would be sucked down the pipes.



Geo Pic
I guess the most important part of the lock is the lock gates, since they keep the water at different levels. I remember reading somewhere that the mass of one door of the upper gate of the lock is 193 tonnes while the mass of one door of the lower gate is 298 tonnes.



Mathise Pic
Wow! The lower gate weighs almost twice as much as the upper gate. I wonder why it weighs so much more?



Trig Pic
You should be able to get your clues from the lock cycle simulation diagram above. Get it?





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