(i)[4]
When the force acts up the plane (see Fig. 1), the block stays at rest. Show that $\mu \geq \frac{17}{24}$.
(ii)[2]
When the force acts down the plane (see Fig. 2), the block moves downwards. Show that $\mu < \frac{31}{24}$.
Mathematics 9709 · AS & A Level · Forces and equilibrium
Forces and equilibrium — practice question
A block weighing $7.5\,\text{N}$ is stationary on a plane inclined to the horizontal at angle $\alpha$, where $\tan \alpha = \frac{7}{24}$. The coefficient of friction between the block and the plane is $\mu$. A force of magnitude $7.2\,\text{N}$, acting parallel to a line of greatest slope, is applied to the block.
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