Question Bank • QB_FP_158 NAT • 2 Marks

Section 3: Farm Power

Farm Power

Subtopic: Calculation of power, torque, fuel consumption, heat load and power losses

Question Statement:

A 2WD tractor engine operates at $2000\text{ rpm}$. The total transmission reduction ratio between engine and rear drive wheels in 2nd low gear is $48 : 1$. The rolling radius of the rear drive tires is $0.65\text{ m}$. Assuming zero tire slip, calculate the theoretical forward travel speed in $\text{km/h}$ (round off to 2 decimal places).

Answer Key:

10.21

Step-by-Step Solution & Explanation

Rear axle rotational speed: $N_{\text{axle}} = \frac{N_{\text{engine}}}{i} = \frac{2000}{48} = 41.667\text{ rpm}$ Linear forward speed: $v = 2\pi r N_{\text{axle}} = 2\pi \times 0.65\text{ m} \times \frac{41.667}{60}\text{ rev/s} = 2.836\text{ m/s}$ Converting to $\text{km/h}$: $v = 2.836 \times 3.6 = 10.21\text{ km/h}$ Acceptable range: $9.9 - 10.5\text{ km/h}$.
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