A car plunges into a lake (water density 𝜌 = 1000 kg m-3). Using the steps below, calculate the resultant hydrostatic force on the door, and the distance from the bottom of the door to the point at which the force acts. Discuss if someone could open the door and describe the what the effect would be of opening a window. Note that the door is hinged at 𝐶𝐷.
i. Using the standard table method, find the
a. Position of the centroid (𝑥𝑐, 𝑦𝑐), its depth ℎ𝑐 and
b. second moment of area 𝐼𝑐 about the horizontal axis through the centroid
of the door by splitting it into rectangles, triangles and quarter-circles.
ii. Compute the hydrostatic force on the door using 𝐹 = 𝜌 𝑔 ℎ𝑐 𝐴. iii. Find the depth of the centre of pressure using ℎ𝑃 = ℎ𝑐 + ℎ𝐼𝑐𝑐𝐴.
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