The speed a car reaches going down a ramp isn't a single number; it depends on the ramp's length and steepness. Ignoring friction and air resistance, a car's acceleration is determined by gravity. On a 45-degree ramp, a car could theoretically reach speeds over 60 mph (97 km/h) in just a few seconds. However, real-world factors like tire grip, drivetrain drag, and air resistance significantly limit this maximum speed.
The primary force at work is gravity. The steeper the ramp (measured by its angle of inclination), the greater the component of gravity pulling the car forward. A longer ramp allows more time for the car to accelerate, leading to a higher final speed at the bottom. It's a basic physics principle of converting potential energy into kinetic energy.
The theoretical maximum is rarely achieved. Key factors that reduce actual speed include:
- Friction: Rolling resistance from the tires and internal friction from the drivetrain (especially if the car is in neutral versus in gear) act against the motion.
- Traction: The tires must grip the ramp surface. On a slippery or loose surface, the wheels may skid, limiting acceleration.
- Aerodynamic Drag: As speed increases, air resistance becomes a major restraining force, eventually balancing the force from gravity and preventing further acceleration.
The following table illustrates the theoretical speed achieved on a perfectly smooth, frictionless ramp of a given length, starting from rest.
| Ramp Angle (Degrees) | Ramp Length (feet) | Theoretical Speed at Bottom (mph) |
|---|
| 15° | 100 | 27 |
| 30° | 100 | 38 |
| 45° | 100 | 47 |
| 15° | 500 | 60 |
| 30° | 500 | 85 |
| 45° | 500 | 106 |
For safety, never attempt this. The forces involved make it extremely dangerous to control a vehicle at high speeds on a confined ramp, with a high risk of losing control or failing to stop at the bottom.
