Which of the following statements regarding the three-dimensional force components acting on a tractor-drawn mouldboard plough is/are CORRECT?
Options:
(A) Draft is the horizontal force component acting parallel to the direction of forward motion
(B) Side force acts perpendicular to the line of motion in the horizontal plane and is primarily resisted by the landside against the furrow wall
(C) Vertical force is perpendicular to the ground plane and is typically directed downwards into the soil under dull share points
(D) Specific draft decreases with an increase in forward operating speed due to soil fluidization
Answer Key:
A, B
Step-by-Step Solution & Explanation
- **Statement A is correct:** Draft ($F_x$) is defined as the force component collinear with the machine centerline and opposite to travel direction.
- **Statement B is correct:** Lateral soil reactions against the curved mouldboard push the plough towards the unploughed land, which is counterbalanced by the landside bearing against the unploughed furrow wall.
- **Statement C is incorrect:** For a sharp plough bottom with suction, vertical force is directed downwards (implement sucked into ground); however, dull shares with worn bottoms generate an UPWARD vertical reaction from the furrow sole that opposes penetration.
- **Statement D is incorrect:** According to the Gorjatchkin equation ($D = f G + k a b + \epsilon a b v^2$), specific draft strictly increases with speed due to the kinetic energy required to accelerate soil particles.