月日题目物理.doc

An engineer's square is in the shape of two uniform rectangular pieces of metal joined as shown in the diagram. The mass of BCDE is3 times the mass of modeling each rectangle asa uniform lamina calculate the distance of the center of mass of the square (a)from AC (b)From CD The square is placed ona peg at F. By modelling the square asa lamina freely suspended from F,calculate the angle between FE and the vertical when the square hangs in two assumptions you have made when using this model to calculate the angle. AB=20cm AG=5cm CD=15cm ED=4cm The engineer's square described in the last question is placed ona rough plane inclined at angle ? to the horizontal as shown in the diagram Find the maximum value of? if the square is to remain in equilibrium. The square is now placed on the inclined plane as shown in the second diagram Determine whether equilibrium is possible (a) when ?=10 °; (b)when ?=30 °