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Consider a particle moving along x-axis. Its distance from origin O is described by the co-ordinate x which varies with time. At a time t_(1), the particle is at point P, where its co-ordinate is x_(1) and at time t_(2), the particle is at point Q, where its co-ordinate is x_(2). The displacement during the time interval from t_(1) to t_(2) is the vector from P to Q, the x-component of this vector is (x_(2) - x_(1)) and all other components are zero. It is convenient to represent the quantity x_(2) - x_(1) the change in x by means of a notation Delta, thus Delta x = x_(2) - x_(1) and Delta t = t_(2) - t_(1). The average velocity bar(V) = (x_(2) - x_(1))/(t_(2) - t_(1)) = (Delta x)/(Delta t) The resistive force suffered by a motor boat is proportional to v^(2), where v is instantaneous velocity. The engine was shut down when the velocity of the boat was v_(0). Find the average velocity at any time t. |
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Answer» `(v_(0) + v)/(2)` `F = -Kv^(2)` `m (dv)/(dt)` or `mv (dv)/(DS) = - kv^(2)` `rArr v (dv)/(dt) = - cv^(2)` `rArr int_(v_(0))^(v) (dv)/(v) = - C int_(0)^(s) ds` |
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