A ground retaining wall is shown in Fig. 9-36a. The ground, particularly when wet, can exert a significant force on the wall. (a) What force produces the torque to keep the wall upright? (b) Explain why the retaining wall in Fig. 9-36b would be much less likely to overturn than that in Fig. 9-36a.
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If the wall overturns, it rotates around the pivot point in the picture. We can write the torques according to this pivot point.
F; force exerted by the ground to the wall.
dF; the perpendicular distance from force to pivot point.
G; the weight of the wall.
dG; the perpendicular distance from weight to pivot point.
The torque of force F. This torque is counterclockwise about pivot point , and this torque can overturn the wall.
The torque of weight W of the wall. This torque is clockwise around pivot point, this torque can keep the wall upright.
If the wall overturns