1 / 9

Viscosity

Viscosity. Fluid Resistance. An object moving through or on a fluid meets resistance. Force causes the fluid to move. The velocity is proportional to the force. F. v x. Velocity Gradient. The resistance tends to keep the fluid in place. Law of inertia

lepore
Download Presentation

Viscosity

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Viscosity

  2. Fluid Resistance • An object moving through or on a fluid meets resistance. • Force causes the fluid to move. • The velocity is proportional to the force. F vx

  3. Velocity Gradient • The resistance tends to keep the fluid in place. • Law of inertia • The fluid moves most near the object and least farther away. • This is a velocity gradient. F vx y

  4. Law of Viscosity • Newton combined these two proportionalities. • This is the law of viscosity. • A is the area of the solid sliding on the fluid • The constant h is the dynamic viscosity and depends on the type of fluid. F vx y

  5. Flow in a tube is affected by sides in all directions. The relationship between velocity and distance is The total volume flow rate is Poiseuille’s Law r P1 vx P2 L

  6. Drag • Kinetic friction is a constant force. • If there is a net force an object would accelerate forever • Air resistance causes a friction called drag. • At low velocity drag is proportional to velocity, Fd = bv • At higher velocity drag goes as velocity squared, Fd = cv2 • The direction of drag force is opposite to the velocity.

  7. Falling Leaves • The drag coefficient depends on the surface area. • Large surfaces – high drag • Leaves • Feathers • Papers • Small surfaces – low drag • Stones • Balls • Bullets

  8. Drag Force • Objects falling through a fluid reach terminal velocity. • For low speeds this is due to viscocity. • Stokes’s Law describes the drag force. Fd Fb Fg

  9. Terminal Velocity • An object may fall through the air at constant velocity. • By the law of inertia the net force is zero. • The force of drag must balance the force of gravity. • This velocity is called the terminal velocity. Fg = -mg

More Related