types of friction

here in this presentation i explain the types of friction and their examples. and i explain world without friction is like this in video.

1. Group member Name:- 1) Ram bhavesh (150210119085) 2) Vaja akhil (150210119121) 3) Vala vivek (150210119123) Subject :- mechanics of solids Topic :- friction Government Engineering college Bhavnagar-(021)

2. What is Friction? Friction is a force between two surfaces that are sliding, or trying to slide across one another, for example when you try to push a toy car along the floor. Friction always works in the direction opposite from the direction the object is moving, or trying to move. It always slows a moving object down. Moving Friction

3. Free Body Diagram Normal Force F N Friction Force f f Applied Force F Gravity Force F g F g = mg F N = F g f f = F

4. Angle of repose   When granular material is heaped, there exists a limit for the inclination of the surface. Beyond that angle, the grains start rolling down. This limiting angle upto which the grains repose (sleep) is called the angle of repose of the granular material. Significance of Angle of repose: The angle that an inclined plane makes with the horizontal, when the body supported on the plane is on the verge of motion due to its self -weight is equal to the angle of repose. Angle of repose is numerically equal to Angle of limiting friction

5. Five Types of Friction Rolling Friction Static friction Kinetic friction Sliding Friction Fluid Friction

6. Rolling Friction Rolling friction is friction that occurs between surfaces in motion in which one of the surfaces is a wheel, roller, or ball. Examples: Riding a bike – tires and ground Bowling – ball and lane

7. Static Friction Static friction is friction that occurs when the surfaces in contact are at rest (not in motion). Examples: A book resting on a desk. A potted plant sitting on a sidewalk.

8. Static Friction F N f s F F g The Force of Static Friction keeps a stationary object at rest!

9. Kinetic Friction F N f k F F g Once the Force of Static Friction is overcome, the Force of Kinetic Friction is what slows down a moving object! Motion

10. Sliding Friction Sliding friction is friction that occurs when solid surfaces slide over one another. Examples: Writing – pencil point and paper Combing your hair – surface of comb and strands of hair

11. Fluid Friction The force that tries to slow objects down when they move through a liquid or a gas. It's also known as "drag", or "air resistance". All gases and liquids are fluids. An airplane and a swimmer both experience fluid friction .

12. Law of friction 1. The limiting frictional force f is directly proportional to the normal reaction N exerted by the surface. i.e. f ∝ N or f = m N where m is a constant called coefficient of limiting friction. 2. The kinetic frictional force f is directly proportional to the normal reaction N exerted by the surface. i.e. f’ ∝ N or f’ = m ’ N where m is a constant called coefficient of kinetic friction. Frictional force f Applied force F A Normal reaction N For simplicity, take f = f’ = m N and m = m ’

13. 18 If the surface is smooth, m = 0 ⇒ f = 0 N Coefficient of friction depends on the two contacting materials. For simplicity, take f = f’ = m N and m = m ’ Rubber Concrete (Dry) m = 0.6 – 0.85 Rubber Concrete (Wet) m = 0.45 – 0.75 Frictional force does not depend on the area of contact of the surfaces.

14. A world without friction is like this !!