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The flying puck

A hockey puck with a mass of 0.170 kg is resting over a hole on a table, as shown in the figure. Suddenly, a prankster shoots at it from below with a vertical water jet issuing from a hose nozzle with a diameter of 10 mm.
a) Estimate the minimum water speed for the puck to take off.
b) If the actual water speed has twice the value computed in (a), determine the initial acceleration of the puck and its ratio to the gravitational acceleration.
c) If the water jet is switched-off 0.5 s after it first hits the puck, determine the speed of the puck at that time, assuming that the jet maintains its speed constant as in (b) during that time and neglecting friction with air.
d) Formulate a differential equation that describes the motion of the puck after the jet is switched off, neglecting friction with air; determine the minimum water jet speed for the puck to hit the ceiling, which is at a height of 5 m above the puck.


Contributed by Stavros Tavoularis, Department of Mechanical Engineering, University of Ottawa, Ottawa, Canada.

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