Gravity in video games is a rule that controls how fast characters, objects, and projectiles speed up as they fall. Real Earth gravity is about 9.8 m/s^2, but many games use stronger or weaker values to make movement feel exciting and responsive. A platformer may use high gravity so jumps snap back to the ground quickly, while a sci-fi shooter may use lower gravity to create floaty movement.
Comparing game gravity to real gravity shows how physics can be adjusted for fun while still following clear patterns.
Key Facts
- Earth gravity near the surface is g = 9.8 m/s^2 downward.
- Vertical velocity changes according to vf = vi + at, where a is usually the game gravity.
- Vertical position can be modeled by y = yi + vi t + 0.5 a t^2.
- Maximum jump height for upward launch speed v is h = v^2/(2g) if air resistance is ignored.
- Time to reach the top of a jump is t = v/g when upward is positive and g is positive downward.
- Terminal velocity is the maximum falling speed when a game caps fall speed or when drag balances gravity.
Vocabulary
- Gravity
- Gravity is the acceleration that pulls objects downward toward a planet, surface, or chosen game direction.
- Acceleration
- Acceleration is the rate at which velocity changes over time.
- Jump arc
- A jump arc is the curved path a character follows while moving upward and then falling back down.
- Terminal velocity
- Terminal velocity is the highest falling speed an object reaches when acceleration is limited by drag or by a game engine.
- Game feel
- Game feel is how responsive, satisfying, and believable controls and motion seem to the player.
Common Mistakes to Avoid
- Assuming all games use real Earth gravity. Many games use values like 20 to 30 m/s^2 because realistic jumps can feel slow on a screen.
- Confusing gravity with jump speed. Gravity controls how quickly the character accelerates downward, while jump speed controls the initial upward launch.
- Ignoring units when comparing games. A value like 25 only means 25 m/s^2 if the game scale and time units are defined that way.
- Thinking terminal velocity is the same as gravity. Gravity is an acceleration, while terminal velocity is a maximum speed that falling objects stop exceeding.
Practice Questions
- 1 A character jumps upward with an initial vertical speed of 12 m/s in Earth gravity, g = 9.8 m/s^2. How long does it take to reach the top of the jump?
- 2 A platform game uses gravity g = 25 m/s^2 and a jump speed of 10 m/s. Ignoring air resistance, what is the maximum jump height?
- 3 A moon level uses lower gravity than a normal level but keeps the same jump speed. Explain how the jump height, time in the air, and player control would feel different.