Question

3. A uniform board with a weight of 240N and a length of 20m rests horiatally supports as shown. Support A is under the left end of the board, while support B is 15mfrom left end a) Draw free body diagram for the board wit all the forces?2points b) What are the conditions for equilibrium? 2 points c) Find two support forces by using equilibrium conditions? 3 points d) If you have only one support to balance the uniform board but you use block of mass 3.0kg on top of the right end of the board, what will be the balance distance to support from left side of the board? 4 points

Answer 1

Given that A uniform board with weight = 240 N length = 2 m a) b) i) Net force on the board must be �O� ii) Net Torque on the board must b zero c) N_1 + N_2 = 240 rightarrow (1) Taking moment about point A 240 times 1 - 1.5 times N_2 = 0 rightarrow (2) from eq (1) & (2) N_1 = 80 N N_2 = 160 N d) Net force on the board is zero R = 240 + mg = 240 + 3 times 9.8 R = 269.4 rightarrow (1) Net Torque on the board is zero R_x - 240 times 1 - 3.0 times 9.8 times 2 = 0 x = 1.109 m