16.. Forces and Shear Stress in Fluids

Try these first

1. 1.

   Define shear stress.

   Hint

   Think about forces acting along surfaces.

2. 2.

   What does viscosity measure?

   Hint

   Consider how easy it is for liquids to flow.

3. 3.

   What is shear stress?

   • Force per unit volume
   • Force per unit area
   • Pressure per unit area

   Hint

   Think about what stress means in physical terms.

4. 4.

   True or False: Viscosity measures how well a fluid can resist deformation.

   • True
   • False

   Hint

   Recall the definition of viscosity.

5. 5.

   A scale model of a boat has a length of 0.8 m and is tested in water. Given that the dynamic viscosity of water is 1 mPa.s, and you are tasked to find the Reynolds number for a prototype boat of length 20 m at the same speed of 4 m/s.

   Hint

   Use standard water density of approximately 1000 kg/m³.

6. 6.

   An object is moving through a fluid at a velocity where viscous forces equal inertia forces. If the object has a diameter of 10 cm and is experiencing a shear stress of 3 Pa, calculate the force exerted on the object by the fluid.

   Hint

   Don’t forget to convert diameter into meters.