explain how a parachutist reaches a constant speed using the concept of terminal velocity.

1 - parachutist is in plane, they are stationary so according to Newton's first law the forces acting on them (weight downwards and reactionary force upwards) are equal. 2 - parachutist leaves the plane. Having jumped out they are now falling due to their weight (mg) which is much bigger than the air resistance acting upwards. Because of this their net force is acting downwards, meaning they accelerate. (Newton's second law, F = ma).3 - they reach terminal velocity because as they are accelerating the air resistance acting on them increases until it balances the weight downwards. Since all forces are balanced they are no longer accelerating and have reached terminal velocity. (Newton's first law).(Diagrams accompany this explanation).