Analyzing forces in equilibrium

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Analyzing forces in equilibrium

  1. 1. AnalyzingPhysics Form 4
  2. 2. Forces in Equilibrium. remains stationary (if • The principle of thethe object is stationary) forces in equilibrium• (ii) moves at a constant states, velocity ( if the object is • “When forces act upon moving) an object , the object is said to be in a state of equilibrium when the resulting force acting on the object is zero (no net force acting upon it) ”
  3. 3. Examples Forces in EquilibriumWeight = Normal reaction Buoyant force = Weight Weight = Normal reaction Weight = Tension
  4. 4. Examples Forces in Equilibrium Weight = Lifting force Weight = Normal reactionPulling force = Frictional force Driving force = Dragging force
  5. 5. Resultant force Force is a vector quantity and hence it has magnitude and direction. Two or more forces which act on an object can be combined into a single force called the resultant force. If two forces are in same line, we simply add the forces if both pull or push together; subtract them if one is in the opposite direction
  6. 6. Two Forces in Equilibrium P + Q=0 P =-Q
  7. 7. Three Forces in Equilibrium PQ R
  8. 8. 3 forces in balance
  9. 9. Triangle method
  10. 10. Parallelogram methodTwo forces of 40N and 60 N act at 600 to each other at a point as representedbelow 1. Choose a scale Suppose we let 2cm represent 10N. Then an 8cm line represents the 40N force and a 12cm line represents the 60N force. Draw these lines with a 600 angle between them:
  11. 11. 2. Complete the parallelogram
  12. 12. 3. Draw the diagonal from the point of application of the forces The diagonal labelled R represents the resultant force - measure this and convert its length to newtons:Diagonal R = 17.4cm, so the resultant force R = (17.4/2)*10 = 87N 4. Measure a suitable angle: The angle A = 230. Thus, the resultant of the two original forces is a force of size 87N acting at 230 to the 60N force
  13. 13. Resolution of forces• is an angle between the force F to the horizontal line•the sign of the force depend on the quadrant where the force , F is placed Fx = F cos  Fy = F sin  A force can be resolved into two components, that is, (i) the horizontal component, Fx and (ii) the vertical component , Fy
  14. 14. Inclined plane A = W sin  B = W cos 
  15. 15. exampleFind the values of Px and Py for the following figures.
  16. 16. Figure shows a stationary wooden block ofmass 50 g which is placed on a inclined planethat is at an angle of 40o to the horizontal.What is the magnitude of the weight parallelto the inclined plane

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