A rear wheel driven tractor weighing 20 kN has 40 percent of its weight supported by the front wheels. The tractor is pulling a trailed plough with a forward speed of 5 km h⁻¹ on flat land. The plough exerts a drawbar pull of 8.0 kN with the line of pull making an angle of 15° with the horizontal in the vertical plane. The drawbar hitch height is 500 mm. If the wheel slip is 20 percent and the coefficient of rolling resistance is 0.04, the tractive efficiency of the tractor is
Options:
(A) 92.39 %
(B) 87.17 %
(C) 73.96 %
(D) 21.79 %
Official Answer Key:
C
Step-by-Step Solution & Explanation
Standard traction-theory relation: Tractive efficiency = [(μ−f)/μ]×(1−slip), where μ is the coefficient of traction (from Q84) and f is the coefficient of rolling resistance. TE = [(0.50−0.04)/0.50]×(1−0.20) = (0.46/0.50)×0.80 = 0.92×0.80 = 0.736 = 73.6%, matching option (C) 73.96% within rounding.
Section 4 — Soil and Water Conservation Engineering
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