Real-World Examples of Stokes' Law in Action

📚 Quick Study Guide

🔍 Stokes' Law: Describes the drag force ($F_d$) on a spherical object moving through a viscous fluid. 🧪 Formula: $F_d = 6 \pi \eta r v$, where:
• 🍎 $\eta$ is the dynamic viscosity of the fluid.
• 🍇 $r$ is the radius of the sphere.
• 🍋 $v$ is the velocity of the sphere.
💡 Key Points:
• 🥝 Applicable for small, spherical objects at low Reynolds numbers.
• 🍓 Drag force is directly proportional to viscosity, radius, and velocity.
• 🍊 Used in various applications like sedimentation, falling ball viscometers, and aerosol science.

Practice Quiz

1. What does Stokes' Law primarily describe?
1. A) The buoyant force on an object.
2. B) The drag force on a spherical object.
3. C) The gravitational force on an object.
4. D) The electrostatic force on an object.


2. Which of the following factors does NOT directly affect the drag force according to Stokes' Law?
1. A) The viscosity of the fluid.
2. B) The radius of the sphere.
3. C) The velocity of the sphere.
4. D) The density of the sphere.


3. In the Stokes' Law equation, $F_d = 6 \pi \eta r v$, what does $\eta$ represent?
1. A) The density of the fluid.
2. B) The radius of the sphere.
3. C) The dynamic viscosity of the fluid.
4. D) The velocity of the sphere.


4. Stokes' Law is most accurate under which condition?
1. A) High Reynolds numbers.
2. B) Turbulent flow.
3. C) Low Reynolds numbers.
4. D) Highly elastic fluids.


5. Which real-world application utilizes Stokes' Law?
1. A) Calculating lift on an airplane wing.
2. B) Designing suspension bridges.
3. C) Measuring the viscosity of liquids using a falling ball viscometer.
4. D) Predicting weather patterns.


6. If the radius of a sphere is doubled, how does the drag force change according to Stokes' Law, assuming all other factors remain constant?
1. A) It is halved.
2. B) It remains the same.
3. C) It is doubled.
4. D) It is quadrupled.


7. What happens to the drag force if the viscosity of the fluid increases, according to Stokes' Law, with all other parameters held constant?
1. A) The drag force decreases.
2. B) The drag force remains the same.
3. C) The drag force increases.
4. D) The drag force oscillates.