Question Bank • QB_EXP_FM_MB_002 NAT • 2 Marks

Section 2: Farm Machinery

Primary Tillage: Mouldboard Ploughs & Forces

Subtopic: Specific draft calculation

Question Statement:

A 4-bottom mouldboard plough with each bottom having a cut width of $30\text{ cm}$ operates at a depth of $15\text{ cm}$ with a forward speed of $4.4\text{ km/h}$. If the unit soil draft is $5.0\text{ N/cm}^2$, the drawbar power required is ________ $\text{kW}$ (round off to two decimal places).

Answer Key:

11.00

Step-by-Step Solution & Explanation

1. Furrow cross-sectional area per bottom: $A_1 = 30 \times 15 = 450\text{ cm}^2$ Total cross-sectional area for 4 bottoms: $A = 4 \times 450 = 1800\text{ cm}^2$ 2. Total draft force: $D = A \times \text{unit draft} = 1800 \times 5.0 = 9000.0\text{ N}$ 3. Forward velocity: $v = 4.4\text{ km/h} = \frac{4.4}{3.6} = 1.22\text{ m/s}$ 4. Drawbar power: $P = \frac{D \times v}{1000} = \frac{9000.0 \times 1.22}{1000} = 11.00\text{ kW}$
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