Question Bank • QB_FM_081 NAT • 2 Marks

Section 2: Farm Machinery

Farm Machinery

Subtopic: Soil tillage

Question Statement:

A rotavator has a rotor diameter of $450\text{ mm}$ and rotates at $240\text{ rpm}$. The tractor moves forward at $3.6\text{ km/h}$. Calculate the kinematic index $(\lambda = v_{\text{periph}} / v_{\text{forward}})$ of the rotavator.

Answer Key:

5.65

Step-by-Step Solution & Explanation

Forward speed of tractor: $v_f = 3.6\text{ km/h} = \frac{3.6}{3.6} = 1.0\text{ m/s}$ Peripheral speed of rotor blade tip: $v_p = \frac{\pi D N}{60} = \frac{\pi \times 0.45 \times 240}{60} = 1.8 \pi \approx 5.655\text{ m/s}$ Kinematic index: $\lambda = \frac{v_p}{v_f} = \frac{5.655}{1.0} = 5.655$
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