Question

Problem 3.5 Consider the L-shaped beam illustrated in Figure 3.34. The beam is mounted to the wall at A, the arm AB extends in the z direction, and the arm BC extends in the x direction. A BE force E is applied in the z direction at the free-end of the beam. (a) If the lengths of arms AB and BC are a and b, respectively and the magnitude of the applied force is F, observe that the position vector of point C relative to point A can be written as -bi+ak and the force vector can be expressed as E Fk wherei j, and k are unit vectors indicating positive x, y, and Figure 3.34 Problem 3.5 z directions, respectively (b) Using the cross product of position and force vectors, deter- mine an expression for the moment generated by E about A in terms of a, b, and F. (c) If a b 30 cm and F 20 N, calculate the magnitude of the moment about A due to F Ansuers: (b) MA -b F i (c) MA 6 N-m

Answer 1

tohs (eY) we have F-2モト,