Question

Useful soil reaction forces on a tractor–drawn mould board plough are 2.0 kN (longitudinal), 0.9 kN (transverse), and 0.6 kN (vertical). Soil–metal friction angle is \(25^\circ\). Neglecting implement weight and vertical soil reaction, estimate the draft (round off to one decimal place).

Hint:

Draft = horizontal force + side force\(\times \tan \phi\), where \(\phi\) is the soil–metal friction angle.

Answer 1

Correct Answer: 2400

Longitudinal force = 2.0 kN
Transverse force = 0.9 kN
Vertical force = 0.6 kN (ignored as per the question) Soil–metal friction adds an additional resistance:
\[ F_f = F_T \tan(25^\circ) \] \[ F_f = 0.9 \times 0.466 = 0.419\ \text{kN} \] Draft:
\[ D = 2.0 + 0.419 = 2.419\ \text{kN} \] \[ D = 2419\ \text{N} \]