Terminal Velocity

This lesson covers the forces acting on falling objects and the concept of terminal velocity — as required by the Edexcel GCSE Physics specification (1PH0), Topic 2: Motion and Forces. You need to understand how the balance between weight and air resistance changes as an object falls, and what determines the terminal velocity of different objects.

---

Forces on a Falling Object

When an object falls through a fluid (such as air or water), two main forces act on it:

1. Weight (W) — the gravitational force pulling the object downward. Weight = mass × gravitational field strength (W = mg).
2. Air resistance (or drag, R) — the frictional force from the fluid acting upward, opposing the motion.

Key Points

• Weight is constant (assuming we stay near the Earth's surface where g ≈ 9.8 N/kg).
• Air resistance increases as the speed of the object increases.
• At the moment of release (from rest), air resistance is zero because the object is not yet moving.