At what speed does air drag becomes important?

Question

Imagine an object that wants to move at a speed $v$ trough a fluid.
I was thinking that when i ride a bike, there is generally a speed at which air drag becomes a problem, but if i ride slow i does not affect the movement that much, making me think that riding slow is more efficient in the long term.
What is the criteria used to determine if the drag from the fluid is important or not?

Prada · Accepted Answer

Here are two graphs from Sheldon Brown. The first one shows Force and the second one shows power requirements vs different velocities.
You can see at roughly 12kmph rolling resistance is same as drag. After that drag starts to increase much faster (proportional to $v^2$)

Bob D · Answer

What is the criteria used to determine if the drag from the fluid is
important or not?

Air drag generally varies as the square of the speed. So, clearly, it becomes very important the greater the speed.
Hope this helps.

At what speed does air drag becomes important?

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