A disk mower operated by tractor PTO has six discs, swath 0.4 m per disk. Specific energy for cutting is 2.1 kJ m⁻²; specific power losses (air, stubble, gear train friction) are 2 kW m⁻¹ of cutting width. Mower with tractor requires a propelling force of 2 kN. Total power required for mowing in kW at forward speed 3 km h⁻¹ is
Options:
(A) 6.47
(B) 7.57
(C) 8.33
(D) 10.67
Official Answer Key:
D
Step-by-Step Solution & Explanation
Total swath W = 6×0.4 = 2.4 m. Speed v = 3 km/h = 0.833 m/s. Cutting power = specific energy × width × speed = 2.1 kJ/m² × 2.4 m × 0.833 m/s = 4.20 kW. Loss power = 2 kW/m × 2.4 m = 4.80 kW. Propelling power = F×v = 2 kN × 0.833 m/s = 1.67 kW. Total = 4.20+4.80+1.67 = 10.67 kW.
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