(a(i))[2]
Fig. 1.1 shows a helicopter that is motionless at a height of 1500 m above the ground. State the two conditions needed for the helicopter to stay in equilibrium.
(a(ii))[2]
Calculate the change in the gravitational potential energy of the helicopter as it rises from the ground to 1500 m.
(b(i))[3]
On Fig. 1.2, choose a point on the graph where the acceleration is: zero, marked '1'; negative, marked '2'; decreasing, marked '3'.
(b(ii))[4]
Explain, in terms of forces, the changes in motion that occur from the moment the parachutist leaves the hot-air balloon up to point A.