For a two-wheel drive rear-wheel-assisted tractor pulling a heavy horizontal draft load on level ground, which of the following mechanical phenomena occur?
Options:
(A) Dynamic weight transfers from the front axle to the rear axle
(B) The normal reaction on the rear driving wheels increases
(C) The normal reaction on the front steering wheels decreases
(D) The tractor is at risk of rearward flip-over if the rear reaction becomes zero
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
1. Moments taken about the rear axle contact point show that the horizontal pull $P$ at height $h$ creates an overturning moment $P \times h$.
2. This overturning moment reduces front axle reaction: $R_f = R_{f0} - \frac{P h}{L}$. Hence normal reaction on front wheels decreases (Statement C is True).
3. By vertical equilibrium ($R_f + R_r = W$), the normal reaction on the rear wheels increases by the exact same amount: $R_r = R_{r0} + \frac{P h}{L}$ (Statements A and B are True).
4. Rearward flip-over (rearing) occurs when the front reaction $R_f$ drops to zero, NOT when rear reaction becomes zero. (Statement D is False)