Physics The rate of change of velocity per unit of time
Acceleration conversion rates
1 Meter per second squared = 0.44704 Miles per hour per second
Standard gravity = 9.80665 Meters per second squared
1 Gal = 0.01 Meters per second squared
1 Foot per minute per second = 0.00508 Meters per second squared
Acceleration is the rate of change in velocity in regard to time (velocity, rather than speed, because acceleration and velocity are vector quantities, whereas speed is scalar). The SI unit (International System of Units) for acceleration is meter per second squared (m/s2).
Multiples of the value for Standard gravity can be used to formulate g-forces; 9.80665 m/s2 is equal to 1 g. In order to quantify that, humans can sustain g-forces roughly in the range of -3 to 9*. Over short periods of time, people can withstand values higher than this. The peak impact of a car crash can generate more than 100g, without permanent damage.
*Pilots can withstand 9g by undertaking high g training and wearing g suits, to retain blood flow to their brains.
The gal, being a unit 1% the magnitude of a meter per second squared, is used to measure variations in gravity. Famed Italian polymath Galileo Galilei is the origin of the name, gal.