The diagram shows a vertical cross-section ABCD of a surface. The parts AB and CD are straight and have lengths 2.5 m and 5.2 m respectively. AD is horizontal, and AB is inclined at 60° to the horizontal. The points B and C are at the same height above AD. The parts of the surface containing AB and BC are smooth. A particle P is given a velocity of 8 m s^-1 at A, in the direction AB, and it subsequently reaches D. The particle does not lose contact with the surface during this motion.

1. Find the speed of P at B.
2. Show that the maximum height of the cross-section, above AD, is less than 3.2 m.
3. State briefly why P’s speed at C is the same as its speed at B.
4. The frictional force acting on the particle as it travels from C to D is 1.4 N. Given that the mass of P is 0.4 kg, find the speed with which P reaches D.