Question

The soil forces acting upon a mould board plough bottom resulting from the operations of cutting, pulverising, lifting, and inverting the furrow slice are 2.2 kN, 1.0 kN, and 0.8 kN along longitudinal, transverse, and vertical directions, respectively. The coefficient of soil-metal friction in the friction phase is 0.3. What will be the estimated draft, neglecting the effects of weight of the implement and the vertical reaction?

• A. 1460 N
• B. 1660 N
• C. 2440 N
• D. 2500 N

Hint:

Frictional force caused by the side force acts opposite to the direction of motion, directly adding to the longitudinal draft requirement:
\[ 2200\text{ N} + (0.3 \times 1000\text{ N}) = 2500\text{ N} \]

Answer 1

The Correct Option is D

Step 1: Identify the direct component of draft.
The longitudinal force of 2.2 kN already acts in the direction of travel, so it contributes directly and fully to the draft.
Step 2: Decide which side force produces friction against the furrow wall.
The transverse force of 1.0 kN presses the landside of the plough against the unploughed furrow wall, and this contact generates a sliding friction force equal to \( \mu \times 1.0 = 0.3 \times 1.0 = 0.3 \text{kN} \) that opposes forward motion.
Step 3: Exclude the vertical force as instructed.
The question explicitly says to neglect the effect of the vertical reaction, so the 0.8 kN vertical component is left out of the friction calculation entirely, even though in general it could also contribute to sole friction.
Step 4: Add up the draft.
Total draft \( = 2.2 + 0.3 = 2.5 \text{kN} = 2500 \text{N} \).
\[ \boxed{2500 \ N} \]