6. A sledge of mass 4 kg rests in limiting equilibrium on a rough slope inclined at an angle \(10 ^ { \circ }\) to the horizontal. By modelling the sledge as a particle,
- show that the coefficient of friction, \(\mu\), between the sledge and the ground is 0.176 correct to 3 significant figures.
(6 marks)
The sledge is placed on a steeper part of the slope which is inclined at an angle \(30 ^ { \circ }\) to the horizontal. The value of \(\mu\) remains unchanged. - Find the minimum extra force required along the line of greatest slope to prevent the sledge from slipping down the hill.