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Fluid Resistance
Key point
- When a body moves through a fluid it experiences fluid resistance force
Fluid resistance force is the force a body experiences when traveling through a fluid.
- Directed opposite to the velocity
- Air resistance is a type of fluid resistance
- Reality vs. Theory (in general air resistance is neglected in IB Questions. If not, then it’s stated explicitly that it’s not)
Not in Formula Booklet but important
Fluid resistance equations
- k is a constant – depending on the fluid resistivity
- There is no limit for which the high-speed formula is used over the low-speed formula. It depends fully on the question and common sense
- As higher the velocity – as higher the resistive force
Suppose we drop a ball from some height.
- The ball’s speed increases due to the gravitational acceleration (weight)
- As the speed increases, the fluid resistance increases too (in this case air resistance)
- Fluid resistance increases until it equals the weight of the ball
Terminal speed formula
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