18 N 40 20 cm Figure 7.12 A 40 N 25 N 20 cm Figure 7.13 25 cm Figure 7.14 40 cm Figure 7.15 25 cm 50 N 40 cm 30 cm 50 B 20 N 50 cm 55 25 N 30 N 12 N - B 00 10 N B 65° Review questions 1 Two forces act on a bar as shown in Figure 7.12. What is the net torque about: a) axis A b) axis B? 2 Two forces act on a bar as shown in Figure 7.13. a) What is the net torque about: i) axis A ii) axis B. b) What weight would need to be added to A to give a net torque of 3.5 N m anti-clockwise around axis B? 3. Three forces act on a bar as shown in Figure 7.14. What is the net torque about: a) axis A b) axis B? 4. Three forces act on a bar as shown in Figure 7.15. a) Calculate the net torque about axis A. b) The net torque about axis B is zero. Calculate the vertical component of force F. c) Do you have enough information to calculate the magnitude of force F? Explain your answer. ​