Force And Pressure

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How to teach force & pressure and it's misconceptions

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Force And Pressure

  1. 1. FORCE AND PRESSURE
  2. 2. RELATIONSHIP BETWEEN FORCE AND PRESSURE FRICTION EFFECTS OF FORCE INTRODUCTION FORCE
  3. 3. - playing a guitar - scrubbing the floor - sawing wood - rowing a boat <ul><li>A pull is when we apply a force to </li></ul><ul><li>move an object towards our body </li></ul><ul><li>A force to move an object away from </li></ul><ul><li>our bodies </li></ul>FORCE A force is a push or a pull or both. A force cannot be seen but we can feel and observe the effects of the force. PUSH PULL COMBINATION OF PUSH AND PULL
  4. 4. Pressing the switch Kicking a ball Launching rocket Pushing trolley Knocking a nail
  5. 5. Tug-of-war Raising a flag Pulling a box Opening the door Drawing back a bow
  6. 6. Rowing a boat Scrubbing the floor Sawing wood Playing guitar
  7. 7. Stops a moving object or makes a stationary object moves Change the speed of a moving object Change the direction of a moving object Changes the shape permanently Changes the shape temporarily EFFECTS OF A FORCE
  8. 8. Stretch a rubber band After An object that will return to its original shape and size after being squeezed, pressed, twisted and stretched is elastic After After Press a sponge Squeeze a spring
  9. 9. Drop a glass After After Tear a piece of paper After Crush an empty can An object that will not return to its original shape and size after being squeezed, pressed, twisted and stretched is inelastic MISCONCEPTION???
  10. 10. A solid cannot be compressed or stretched!! CHILDREN’S MISCONCEPTION EXPLANATION The shape of a solid object changes when a force is applied to it whether it’s temporarily or permanently Example: crushing a can – changes the shape permanently
  11. 11. when a force is applied in the opposite direction (or different direction), the moving object will change its moving direction MISCONCEPTION ???
  12. 12. Misconception? A force is needed to keep an object moving with a constant speed Explanation: You do not need forces to move at a steady speed but if you keep the same speed yet change direction, like a moon around a planet, then you have a force acting on you anyway An object will move faster when a force is applied It moves in the same direction as the applied force
  13. 13. <ul><li>A stationary ball will move when it is </li></ul><ul><li>kicked </li></ul><ul><li>Moves in the same direction as the </li></ul><ul><li>applied force </li></ul><ul><li>The moving ball will stop when </li></ul><ul><li>an equal force is applied in the </li></ul><ul><li>opposite direction of its motion </li></ul>MISCONCEPTION ???
  14. 14. Force is a property of an object. An object has force and when it runs out of force it stops moving EXPLANATION an object at rest or in motion will remain in that state unless an external force is applied to the object Newton 1 st Law
  15. 15. FRICTION - Occurs when two surfaces are moving in contact with each other Factors that effect friction Physical condition of the surface Weight of an object <ul><li>Advantages </li></ul><ul><li>enables people to run and walk </li></ul><ul><li>without falling or slipping </li></ul><ul><li>enables us to write on paper </li></ul><ul><li>enables a car to stop when the brakes </li></ul><ul><li>are applied </li></ul><ul><li>enables an object to be stationary </li></ul><ul><li>music instruments can produce sound </li></ul><ul><li>allows vehicles to travel on the road </li></ul><ul><li>without slipping </li></ul><ul><li>Disadvantages </li></ul><ul><li>slows down a moving object </li></ul><ul><li>causes the surfaces of objects </li></ul><ul><li>to wear out </li></ul><ul><li>causes less effectiveness of </li></ul><ul><li>moving machine </li></ul><ul><li>causes heating </li></ul><ul><li>causes sound pollution </li></ul><ul><li>increases cost when worn-out </li></ul><ul><li>objects need to be replaced </li></ul><ul><li>with new ones </li></ul><ul><li>Ways to reduce </li></ul><ul><li>use ball bearing </li></ul><ul><li>use wheel and axle </li></ul><ul><li>use lubricants such as grease </li></ul><ul><li>or oil </li></ul><ul><li>use air cushion </li></ul><ul><li>use roller bearing </li></ul>
  16. 16. MISCONCEPTION??? Friction is only present when something is rubbing against a moving object EXPLANATION Occurs when two surfaces are moving in contact with each other
  17. 17. Examples of friction
  18. 18. RELATIONSHIP BETWEEN FORCE AND PRESSURE <ul><li>AIR PRESSURE </li></ul>BICYCLE PUMP A force is applied to the pump to produce air pressure Applying force Pull and push

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