Representing Terminal Velocity (AQA GCSE Physics)

• A velocity-time graph can show how the velocity of an object changes in time as it reaches terminal velocity
• There are characteristic features of all terminal velocity graphs:
  • The gradient (or slope) of a velocity-time graph represents the acceleration of the object
  • On any terminal velocity graph, the gradient (acceleration) will decrease from being very large down to zero
  • Sometimes the gradient is negative (i.e. showing deceleration, or slowing down)

Debbie the skydiver experiences a large deceleration (her speed decreases suddenly) as soon as she opens her parachute, because of a large resultant force upwards

• The image above shows a skydiver slowing down, due to the large upwards resultant force acting on her
  • At this moment in time, the air resistance is larger than the skydiver's weight (due to the parachute's huge surface area)
  • This results in a large unbalanced force upwards, decelerating the skydiver's descent

• The graph below summarises how a skydiver's velocity changes up to and following the point of opening a parachute:

Graph showing how the velocity of a skydiver changes during descent