Physics II workshop_Part_36

Physics II workshop_Part_36 - initial kinetic plus the work...

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74 Week #7
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75 Work and kinetic energy Introduction The kinetic energy (K) of an object of mass m , moving with velocity v , is defined as K = 1 2 mv 2 . The work done by a net force F net ( x ) in moving the object from an initial position x 0 to a final position x is W = F net ( x ) x 0 x dx If the force acts is one dimension (i.e. along the x -axis in this case), the work is just the area under the curve F net ( x ) vs x , between the limits x0 and x. For a constant force, it is the area of the shaded rectangle. The work–energy theorum tells us that the work done by the force is equal to the change in the kinetic energy of the object: W = K K 0 . Another way of saying this is that the final kinetic is equal to the
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Unformatted text preview: initial kinetic plus the work done: K = K + W . Speed of a car Now try to use these ideas to answer the following questions. A car moves along a straight line in the positive x direction. The net force on the car varies as the car moves, and is plotted as a function of position for two different situations in the graphs. 1. On each graph, shade in the area that represents the work between positions A and B. 2. Is the work positive or negative? 3. At which point is the car moving faster (circle one)? Top graph: A B Bottom graph: A B Explain your reasoning: Force position x x W F net...
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Physics II workshop_Part_36 - initial kinetic plus the work...

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