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work energy power for class ix
- 1. ALLAH IS THEBEST CREATOR OF NATURAL BEAUTY
- 3. What they areDoing?What they are Doing?
- 5. a. What isWork? b. What do you mean by 1J work done. c. Calculate the work done by the man against the gravity d. Compare the man’s work done with another body of same mass when raised through an inclined plane making an angle of 300 with the horizontal plane (length of the stair =3m) Mass of the man 80 Kg Heightofeachstep =10cm= 0.10m Noofstep=20
- 6. WorkWork Work is defined as theproduct of force and displacemen t Therefore Work done W = F x S Displacement F FORCE S Work is the success of the application force on an object which can produce
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- 8. ++VVee WORKWORK DONEDONE Work doneW = F x S cos θ= F S cos θ Displacement F FORCE Applied Below C.G Accepted Displacement S Ssinθ S cos θ 0 ≤ θ >900 Work is the success of the application force on an object which can produce θ Displacement is considered along the same direction of applied force
- 9. A force atsome angle (not 90A force at some angle (not 90OO ) to the direction of) to the direction of movement can be resolved into the horizontalmovement can be resolved into the horizontal component to calculate the work done.component to calculate the work done.
- 10. Variation of workVariationof work withwith θθ W But When W= FSCos 90=0 Displacem ent Scos θ FORCE applied near the bottom Scosθ θ= 90 FORCE applied at the bottom line S Work is the success of the application force on an object which can produce θ Displacement F S If θ
- 11. Negative work DoneNegativework Done S cosθ θ> 90 FORCE applied below C.G 1800 ≤ θ > 900 Work is the success of the application force on an object which can produce Displacem ent S Force Direction If θ>900 Then cosθ= -Ve so. Work = - Ve Accepted Displacement
- 12. Negative work DoneNegativework Done S cosθ θ = 1800 FORCE applied below C.G Work is the success of the application force on an object which can produce Force Direction Accepted Displacement When θ=1800 Then Work W= FS cos1800 W= FS(-1) = -Fs
- 13. This is GlenCanyon Dam on the ColoradoThis is Glen Canyon Dam on the Colorado River between Utah and Arizona.River between Utah and Arizona. The dam is among the tallest in America, soThe dam is among the tallest in America, so you can imagine the tremendous pressure onyou can imagine the tremendous pressure on the water as it moves to generators at thethe water as it moves to generators at the bottom of the dam.bottom of the dam.
- 14. A Complete DefAComplete Defn.n. of WORKof WORK The work done on an object is the magnitude of the applied force multiplied by the parallel distance* through which the force acts. Work = force X distance W = Fs cosθ
- 15. Meaning of paralleldistance…Meaning of parallel distance… the distance moved either in the same(θ=00 ) or opposite (θ=1800 ) direction of the applied force or Part of the displacement (Scosθ) either same or opposite direction of the applied
- 16. Be sure …..Besure ….. 1. For a work Displacement is a must. 2. The part of the movement is considered either in the same or opposite direction of the applied force. 3. When force is resolved into the component force then only that part of force is considered which acts in the same direction of the
- 17. Units of Work:Unitsof Work: W = F S The SI unit of Work W = (Newton)(Meter) W = N•m = Joule
- 18. The JouleThe Joule Joule(J): The SI unit of energy Amount of work done by a force of one Newton when it acts through a distance of one meter: Example: Push a box 8 m across the floor with a force of 100 N performs 800 J of work: m)(Nmeter.newton1(J)joule1 ⋅= JmNmNFdW 800800)8)(100( =⋅===
- 19. H/W: CQ a. Whatis zero work b. Is there any work if you exchange 10 books in between the top shelf to the bottom shelf? c. Calculate the work done to move a book of mass 1kg from 2nd shelf to 3rd shelf ? d. Explain why work is a scalar quantity even though the force and displacement both are vector quantity Total height =2.5 m Shelves are equally spaced
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