Home · IGCSE 0625 · Motion, forces, energy · Terminal velocity · Practice
Extended · Practice questions · Terminal velocity

Balanced, yet still moving.

Six original Cambridge-style Extended questions on the force balance during a fall, why a terminal velocity is reached, the zero-resultant-force condition, and a parachute opening.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
The argument to make

Drag grows until it matches weight.

01
[2 marks]

Define terminal velocity.

  • The constant (maximum) velocity reached by an object falling through a fluid. ✓
  • It occurs when the drag has grown to equal the weight, so the resultant force is zero. ✓
02
Analysis
[3 marks]

An object falls through air. State the two main forces acting on it, and describe how each changes as the object speeds up.

  • Weight acts downward and stays constant. ✓
  • Air resistance (drag) acts upward. ✓
  • The drag increases as the object's speed increases. ✓
03
Analysis
[3 marks]

Explain, in terms of forces, why a falling object eventually reaches a terminal velocity.

  • As the object speeds up, the drag increases. ✓
  • Eventually the drag grows to equal the weight, so the resultant force becomes zero. ✓
  • With no resultant force there is no acceleration, so the velocity stays constant: the terminal velocity. ✓
04
Analysis
[2 marks]

At terminal velocity, state the resultant force on the object and whether it is moving. Explain how both statements can be true at once.

  • The resultant force is zero, and the object is still moving (at constant speed). ✓
  • A zero resultant force means no acceleration, not no motion; balanced forces keep the velocity constant. ✓
05
Analysis
[3 marks]

A skydiver is falling at terminal velocity and then opens a parachute. Describe what happens to the forces and the motion immediately afterward.

  • The parachute greatly increases the drag, so drag is now larger than the weight. ✓
  • There is a resultant force upward, so the skydiver decelerates (slows down). ✓
  • As they slow, drag decreases until it again equals weight, giving a new, lower terminal velocity. ✓
06
Analysis
[2 marks]

Describe the shape of the velocity-time graph for an object dropped from rest that reaches terminal velocity.

  • It rises steeply at first (large acceleration). ✓
  • The curve bends over as the acceleration decreases, then levels off to a horizontal line at the terminal velocity. ✓