Experimental technique
Variables

Jonathon notices two water tanks with holes in them as shown below. He observes that water leaks faster from one tank than the other. He wants to test why this is so.
He designs an investigation to answer the question "Does water leak at a faster rate from a hole that is high above the base of the tank than one that is close to the base?"

What are the factors that will influence the rate at which water leaks from the hole in a vertical tank of water?

-The amount of water in the tank.
- The size and shape of the tank.
-The size of the hole.
-The height of the hole from the base of the tank.

These factors are called variables because they can change the results.

 

We need to investigate how the height of the hole influences the rate at which water escapes?
So we need to set up a controlled experiment. A controlled experiment is one in which every time a test is conducted all variables are kept constant except for one.
So, we setup two drums of water as shown on the right. Each drum must:
- have the same amount of water in it.
- be of identical size and shape.
- have the same size hole.
The only variable that is different in each drum is the height of the hole. This is the variable that we are testing for. When we compare the two drums we see that the flow of water escaping from the hole near the base of the drum is greater than the water flowing from the hole higher up.
This is a fair comparison between the two drums and Jonathon can confidently conclude that the rate of water flow is greater through a hole near the base of the drum than one that is higher.
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