3 A block of mass 8 kg slides down a rough plane inclined at \(30 ^ { \circ }\) to the horizontal, starting from rest. The coefficient of friction between the block and the plane is \(\mu\). The block accelerates uniformly down the plane at \(2.4 \mathrm {~m} \mathrm {~s} ^ { - 2 }\).

1. Draw a diagram showing the forces acting on the block.
2. Find the value of \(\mu\).
3. Find the speed of the block after it has moved 3 m down the plane.