Question Bank • QB_FP_064 NAT • 2 Marks

Section 3: Farm Power

Tractors and Power Tillers

Subtopic: Power transmission systems – gear trains, differential, final drives and power take-off

Question Statement:

A tractor engine operates at $N_{\text{eng}} = 2000\text{ rpm}$. The transmission drivetrain has a selected gearbox reduction ratio of $3.5:1$, a differential crown wheel-to-pinion reduction ratio of $4.0:1$, and a planetary final drive reduction ratio of $3.0:1$. The rear drive tires have an effective rolling radius of $r = 0.70\text{ m}$. Assuming zero wheel slip, the theoretical forward travel speed of the tractor in $\text{km/h}$ is ________ (round off to 2 decimal places). Take $\pi = 3.1416$.

Answer Key:

12.57

Step-by-Step Solution & Explanation

1. Overall drivetrain reduction ratio ($i$): $i = 3.5 \times 4.0 \times 3.0 = 42.0$ 2. Rotational speed of rear axle wheels ($N_{\text{wheel}}$): $N_{\text{wheel}} = \frac{2000}{42.0} \approx 47.619\text{ rpm}$ 3. Forward travel speed ($v$): $v = \frac{2 \pi r N_{\text{wheel}} \times 60}{1000} = \frac{2 \times 3.1416 \times 0.70 \times 47.619 \times 60}{1000} = \frac{12,566.4}{1000} \approx 12.57\text{ km/h}$
← Previous (QB_FP_005) Next (QB_FP_ADV_050) →

Practice In Authentic CBT Exam Interface

Test your skills under authentic timed conditions with live scoring and AIR percentile ranking.

Launch CBT Mock Test