3 A plane is inclined at an angle of \(\sin ^ { - 1 } \left( \frac { 1 } { 8 } \right)\) to the horizontal. \(A\) and \(B\) are two points on the same line of greatest slope with \(A\) higher than \(B\). The distance \(A B\) is 12 m . A small object \(P\) of mass 8 kg is released from rest at \(A\) and slides down the plane, passing through \(B\) with speed \(4.5 \mathrm {~ms} ^ { - 1 }\). For the motion of \(P\) from \(A\) to \(B\), find

1. the increase in kinetic energy of \(P\) and the decrease in potential energy of \(P\),
2. the magnitude of the constant resisting force that opposes the motion of \(P\).