1 / 22

Applications of Newton’s Laws

Applications of Newton’s Laws. Chapter 6 Friction, Strings & Springs Translational Equilibrium TIMED QUIZ – Monday? Over Force Balances, Free Body Diagrams, Friction. Frictional Forces. Friction has its basis in surfaces that are not completely smooth:. Frictional Forces – Kinetic Friction.

larue
Download Presentation

Applications of Newton’s Laws

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. Applications of Newton’s Laws Chapter 6 Friction, Strings & Springs Translational Equilibrium TIMED QUIZ – Monday? Over Force Balances, Free Body Diagrams, Friction

  2. Frictional Forces Friction has its basis in surfaces that are not completely smooth:

  3. Frictional Forces – Kinetic Friction Kinetic friction: the friction experienced by surfaces sliding against one another The static frictional force depends on the normal force: (6-1) The constant is called the coefficient of kinetic friction.

  4. Frictional Forces – Kinetic Friction The kinetic frictional force is also independent of the relative speed of the surfaces, and of their area of contact.

  5. Frictional Forces – Static Friction The static frictional force keeps an object from starting to move when a force is applied. The static frictional force has a maximum value, but may take on any value from zero to the maximum, depending on what is needed to keep the sum of forces zero.

  6. Frictional Forces – Static Friction (6-2) where (6-3) The static frictional force is also independent of the area of contact and the relative speed of the surfaces.

  7. Example 6-1 in Textbook • Salt shaker - 50 g • With vo = 1.15 m/s • Stops in 0.840 m • So vf is? • Value of μk? • Stopping Δt for different vo?

  8. Example 6-1 in Textbook • Part A: Start with Newton’s 2nd Law • How do you know ax?

  9. Example 6-1 in Textbook • Need force balance in y-direction ( for Normal ) • Why do we need the Normal Force on shaker?

  10. Example 6-1 in Textbook • Part B: what is the same? • Use relationship for constant acceleration

  11. Conceptual Checkpoint • 6-1 pg 155

  12. Conceptual Checkpoint 6-1

  13. Conceptual Checkpoint 6-1

  14. Homework Problems • #6, pg 178 ( HONORS ) • #10, pg 178 ( AP )

  15. Strings and Springs When you pull on a string or rope, it becomes taut. We say that there is tension in the string.

  16. Strings and Springs The tension in a real rope will vary along its length, due to the weight of the rope. Here, we will assume that all ropes, strings, wires, etc. are massless unless otherwise stated.

  17. Strings and Springs An ideal pulley is one that simply changes the direction of the tension:

  18. Strings and Springs Hooke’s law for springs states that the force increases with the amount the spring is stretched or compressed: The constant k is called the spring constant.

  19. Translational Equilibrium (6-5) When an object is in translational equilibrium, the net force on it is zero: This allows the calculation of unknown forces.

  20. Translational Equilibrium

  21. Conceptual Checkpoint • 6-2 pg 159 • 6-3 pg 162

  22. Homework Problems • #22, pg 179

More Related