Forces on Roller Coaster Riders: Gravity, G-Forces, and More

Riders experience a combination of real and apparent forces throughout a coaster's course.

Real Forces (Physical Interactions)

• Gravity (Weight): Downward force (mg); constant magnitude, changing direction relative to the rider.
• Normal Force: Seat/track pushes perpendicular to contact surface. Varies with track banking, hills, loops. What you *feel* as "weight."
• Friction: Between wheels and track; opposes motion, causes heating, reduces speed.
• Air Resistance (Drag): Opposes motion; significant at high speeds (>100 km/h).

Apparent/Inertial Forces (In Rider's Non-Inertial Frame)

• Centripetal Force: Real force (from track/seat) directing rider toward curve centre. Magnitude = mv²/r.
• "Centrifugal Force": Fictitious outward sensation in rider's frame; equals centripetal in magnitude.
• Lateral Gs: Side-to-side forces on banked turns or transitions.
• Longitudinal Gs: Forward/backward forces during launch/braking.

Typical G-Force Ranges

• Positive Gs (bottom of drops, loops): +3 to +5 G (up to +6 G on extreme coasters).
• Negative Gs (airtime hills): -0.5 to -1.5 G (weightlessness/ejection sensation).
• Lateral Gs: Usually < ±1.5 G for comfort.

Design Balance

Engineers shape track geometry to deliver thrills (high Gs, airtime) while keeping forces within human tolerance (ASTM F2291 standards) and avoiding injury (greyout/redout, neck strain).