3 A particle, of mass 2 kg , is placed at a point A on a rough horizontal surface. There is a straight vertical wall on the surface and the point on the wall nearest to \(A\) is \(B\). The distance \(A B\) is 5 m . The particle is projected with speed \(4.2 \mathrm {~ms} ^ { - 1 }\) along the surface from A towards B . The particle hits the wall directly and rebounds. The coefficient of friction between the particle and the surface is 0.1 .

1. Determine the speed of the particle immediately before impact with the wall. The magnitude of the impulse that the wall exerts on the particle is 9.8 Ns .
2. Find the speed of the particle immediately after impact with the wall.