1 / 0

Do Now 10/15

Do Now 10/15. Newton’s 1 st law states that objects in motion tend to stay in motion. Why, then, do objects usually slow down and eventually stop? Explain in as much detail as possible. Concept Development 6-1. (pg 1 only). Do Now 10/15/10. Complete Concept Development 6-1.

dung
Download Presentation

Do Now 10/15

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. Do Now 10/15 Newton’s 1st law states that objects in motion tend to stay in motion. Why, then, do objects usually slow down and eventually stop? Explain in as much detail as possible.

  2. Concept Development 6-1

    (pg 1 only)
  3. Do Now 10/15/10 Complete Concept Development 6-1. THEY ARE SITTING HERE
  4. 6.4Friction Friction is a force and affects motion: Friction acts on materials that are in contact with each other. When two solid objects come into contact, the friction is mainly due to irregularities in the two surfaces.
  5. 6.4Friction Rubber against concrete produces more friction than steel against steel, so concrete road dividers have replaced steel rails. The friction produced by a tire rubbing against the concrete is more effective in slowing the car than the friction produced by a steel car body sliding against a steel rail.
  6. 6.4Friction Air resistance is the friction acting on something moving through air.
  7. 6.4Friction The direction of the force of friction always opposes the direction of motion. a. Push the crate to the right and friction acts toward the left.
  8. 6.4Friction The direction of the force of friction always opposes the direction of motion. a. Push the crate to the right and friction acts toward the left. b. The sack falls downward and air friction acts upward.
  9. 6.4Friction think! Two forces act on a book resting on a table: its weight and the normal force from the table. Does a force of friction act as well?
  10. 6.4Friction think! Two forces act on a book resting on a table: its weight and the normal force from the table. Does a force of friction act as well? Answer:No, not unless the book tends to slide or does slide across the table. Friction forces occur only when an object tends to slide or is sliding.
  11. 6.4Friction What factors affect the force of friction between surfaces?
  12. 6.4Friction There are different types of friction:
  13. 6.4Friction There are different types of friction: Static Friction – friction between two objects that are not moving ex. Desk that won’t move You’re in your new college dorm next year and push on a desk that is too heavy to move. It hasn’t moved yet, so that is static friction. What is the value of the friction force compared to the applied force?
  14. 6.4Friction There are different types of friction: Sliding Friction – friction between two objects that slide past one another ex. A box that is sliding You slide a box across the floor and friction pushes against the applied force as it slides. What is the value of the friction force compared to the applied force?
  15. 6.4Friction There are different types of friction: Rolling Friction – friction between two objects that roll past one another ex. A ball rolling down a hill As a ball rolls down a hill, friction acts against its motion.
  16. 6.4Friction Friction is abbreviated, Ff Friction is calculated, Ff = μFN
  17. 6.4Friction μ, (the Greek letter mu), is called the coefficient of friction The coefficient of friction is different for various materials. Rubber Asphalt (Dry) 0.5-0.8 Rubber Asphalt (Wet) 0.25-0.75 Rubber Concrete (Dry) 0.6-0.85 Rubber Concrete (Wet) 0.45-0.75
  18. 6.4Friction Why does the Normal Force affect friction? More closely “pushed” together = more friction
  19. 6.4Friction Example 1 The block below lies at rest, calculate the normal force, Fn. FN= ? Fg = 30 N
  20. 6.4Friction Example 2 The block below lies at rest and has coefficient of sliding friction of 0.45. Calculate the normal force, Fn, and calculate the force of kinetic friction. What is the net force? FN= ? Fapplied = 25 N m = 5 kg Fg=?
  21. 6.4Friction Example 3 The block below is being pulled to the right and has coefficient of sliding friction of 0.40. Calculate the normal force, the force of sliding friction, and the net force acting on the block. FN= ? Applied F = 30 N Friction F = ? Fg = 60 N
  22. 6.4Friction Example 4 A 15.0 kg block is pulled by a horizontal force of 30.0 N along a rough horizontal surface at constant velocity. What is the coefficient of friction?
  23. 6.4Friction Homework: pg 99 #7-9 and #37
More Related