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WHAT ARE SOME FACTORS THAT AFFECT MOTION OF OBJECTS OR BODIES?

WHAT ARE SOME FACTORS THAT AFFECT MOTION OF OBJECTS OR BODIES?. Suppose you will be asked to push a baggage on two surfaces:. Surface A  Glass surface. Surface B  Hollow block surface.

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WHAT ARE SOME FACTORS THAT AFFECT MOTION OF OBJECTS OR BODIES?

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  1. WHAT ARE SOME FACTORS THAT AFFECT MOTION OF OBJECTS OR BODIES?

  2. Suppose you will be asked to push a baggage on two surfaces: Surface A  Glass surface Surface B  Hollow block surface In which surface will it be easier for you push the baggage? surface harder for you to push? Can you explain your answer?

  3. Road A Road B In which surface will it be easier for you to drive? Why?

  4. FRICTION A force on objects or bodies in contact with each other that resists or opposes motion of the objects or bodies relative to each other. A force that exists whenever two surfaces or bodies are in contact whether at rest or moving.

  5. Whenever two surfaces or bodies are in contact whether at rest or moving there exists FRICTION between them. where applied force push or a pull normal force  weight friction force  opposing force to the applied force

  6. There is FRICTION between the road & the tires of automobiles

  7. There is FRICTION between the pen or pencil & your paper

  8. There is FRICTION between two rubbing surfaces

  9. There is FRICTION between your shoes & the ground Can you give other examples of bodies experiencing friction?

  10. WHAT CAUSES FRICTION? Not all Surfaces are smooth or rough! It is caused by the irregularities or interlocking of tiny projections on rubbing surfaces or surfaces in contact.

  11. surface NATURE OF FRICTION • It is parallel to the surface in contact.

  12. NATURE OF FRICTION Direction of Applied force • It opposes motion thus its direction is opposite the direction of motion.

  13. Wooden surface Rough road Concrete road Pimpled face NATURE OF FRICTION • Its amount or magnitude is dependent on the nature and kind of surface in contact.

  14. NATURE OF FRICTION • Its magnitude is affected by the Normal force perpendicular to the surface. Which of the two will experience more friction?

  15. NATURE OF FRICTION • the status of the body in contact with surface – “at rest” or in motion. Which of the two will experience more friction?

  16. Static Frictionarises between two objects or bodies that are in contact but motionless. TYPES OF FRICTION

  17. Kinetic Frictionarises between bodies that in contact & in motion. TYPES OF FRICTION

  18. It increases to counterbalance forces that moves objects or bodies. It serves as a support to moving bodies or bodies at rest. There must be friction so bodies will not slip on surfaces easily. What are the advantages of friction?

  19. It causes fast wear and tear of materials or parts of machines. It may cause over heating in machines. It may dampen motion or slows down motion. What are the disadvantages of friction?

  20. HOW DO WE INCREASE FRICTION ON SURFACES? The use of rubber materials

  21. HOW DO WE INCREASE FRICTION ON SURFACES? The use of lines, designs or marks on surfaces

  22. HOW DO WE INCREASE FRICTION ON SURFACES? The use of spikes on surfaces

  23. HOW DO WE INCREASE FRICTION ON SURFACES? The use of chains on roads

  24. HOW DO WE INCREASE FRICTION ON SURFACES? The use of sand or creating lines on roads

  25. HOW DO WE REDUCE FRICTION ON SURFACES? The use of wheels

  26. HOW DO WE REDUCE FRICTION ON SURFACES? The use of bearings or rollers

  27. HOW DO WE REDUCE FRICTION ON SURFACES? The use of wax, powder etc… on surfaces

  28. HOW DO WE REDUCE FRICTION ON SURFACES? The use of oil, grease & other lubricants on surfaces

  29. HOW DO WE REDUCE FRICTION ON SURFACES? The Use of sandpaper, varnish, paint

  30. HOW DO WE REDUCE FRICTION ON SURFACES? The Use of streamlining

  31. HOW DO WE COMPUTE FOR FRICTION? Static friction ( Fs ): Fs = sN where N  Normal Force s  coefficient of static friction ( constant )

  32. HOW DO WE COMPUTE FOR FRICTION? Kinetic friction ( Fk ): Fk = kN where N  Normal Force k coefficient of kinetic friction (constant) The coefficient of friction is the ratio of the force that maintains contact between an object and a surface and the frictional force that resists the motion of the object.

  33. Estimated coefficients of static & kinetic friction of various materials

  34. Note!If a body or object is being pushed or pulled horizontally on a surface, the normal force ( N ) is simply the weight of the body or object (in Newtons). However, if the mass is given (in kg )the formula would be: Fk = kmg or Fs = smg

  35. PROBLEM 1: A wooden box, which is 250 Newtons, is pushed on a wooden floor. How much friction is present on the surfaces in contact? Suppose the wooden box will remain at rest then how much friction will be exerted on the surface?

  36. Problem 2: A patient weighing 60kg is pushed on a wheel chair along the corridor of a hospital. Suppose the weight of the wheel chair is neglected, and the coefficient between the floor and the wheel chair is 0.8 then how much force is needed to push the wheel chair?

  37. Problem 3: If a force of 80 Newtons is needed to pull a balikbayan box which is 200 Newtons then find the coefficient of friction on the surfaces in contact.

  38. EXERCISE 13: FRICTION # 1 1, 4 & 7 #2  2, 3 & 8 #3  1, 5 & 6 • A man can push a 100 – kg stretcher containing a patient across a wooden floor. Find the coefficient of friction exerted by the two surfaces if frictional force is 200N. • 2. A 45kg man wearing leather shoes stands on a wooden floor. Find the friction exerted on the floor. • 3. Find the force needed to pull a balikbayan box which is 200 Newtons if the coefficient of friction is 0.22. • 4. The tire of a moving 1500kg – truck is in contact with a wet concrete road. Find the force needed to overcome friction. • Find the mass of an object made of steel which is placed on a steel surface if the friction exerted between them is 250 Newtons. • 6. A 30-kg wooden cabinet stands on a wooden floor. Find the amount of friction exerted on the floor. • 7. The tire of a bus which is 1400kg is in contact with a dry concrete road. Find the amount of friction exerted. • 8. Find the mass of a man wearing leather shoes standing on a wooden surface if the force exerted on the surfaces in contact is 200 Newtons.

  39. Application of friction Clinical: “Friction Massage” Friction Massage Therapy for Tendonitis Friction massage basically “scrubs” the fibers of the tendon, aiding recovery. The mechanism is probably just stimulation.

  40. How to do friction massage The action of friction massage is extremely simple: just strum back and forth over the inflamed tendon at the point of greatest tenderness. Your strokes should be perpendicular to the fibres of the tendon — like strumming across a guitar string. Use gentle to moderate pressure with the pads of your fingers or a thumb. Friction massage treatments should be wrapped up by cooling the area down with an application of raw ice. http://saveyourself.ca/articles/frictions.php

  41. Skin Friction http://solutions.3m.com/wps/portal/3M/en_US/SH/SkinHealth/solutions/skin-wound-care/friction/

  42. Use of lubricants Personal lubricants have long been recommended to women to improve the comfort of sexual intercourse and to reduce the risk of vaginal tearing or genital pain, yet strikingly little available data is available on women’s use of lubricants or associated vaginal symptoms. http://www.procto-med.com/why-men-and-women-use-lubricants-during-sex-two-studies/

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