The resultant soil reaction force acting on a single bottom mould board plough has a component of 1200 N acting at an angle of 31° downwards in a vertical plane. This plane is along the direction of travel. Weight of the plough is 620 N. Neglecting the side forces, the magnitude of pull in N would be
Options:
(A) 618
(B) 1028
(C) 1350
(D) 1609
Official Answer Key:
B
Step-by-Step Solution & Explanation
The 1200 N resultant soil reaction acts 31° below the horizontal (in the vertical plane containing the travel direction). Its horizontal component is the draft/pull required to overcome soil resistance: Pull = 1200×cos(31°) = 1200×0.8572 ≈ 1028 N, matching option (B). (Its vertical component, 1200×sin31° ≈ 618 N, nearly balances the plough's own weight of 620 N — a sanity check that the resultant is consistent with near-vertical equilibrium — but this vertical figure is not what the question asks for; option (A) is a distractor built from that vertical component.)
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