The Physics
Hypertextbook
Opus in profectus

# Acceleration

## Summary

• Acceleration is the rate of change of velocity with time.
• As a vector it must be stated with both magnitude and direction.
• Acceleration occurs anytime an object's…
• speed increases
• speed decreases
• direction of motion changes
• Average acceleration
• is measured over a non-zero time interval
• is represented by the symbol aave or a (overline)
• Instantaneous acceleration
• is the limit of average acceleration as the time interval approaches zero
• is the first derivative of velocity with respect to time
• is the second derivative of displacement with respect to time
• is represented by the symbol a (boldface)
• The various forms of acceleration are defined by the following equations…
average
acceleration
 a = Δv Δt
instantaneous
acceleration

a =   lim Δt→0
Δv  =  dv  =  d2s
Δt dt dt2
• The SI unit of acceleration is the meter per second squared [m/s2]
• The standard acceleration due to gravity
• is a natural unit of acceleration
• is represented by the symbol g (roman)
• is equal to 9.80665 m/s2 by definition
• is often rounded to 9.8 m/s2 for convenience
• is sometimes called the unit of "g force" even though it is a unit of acceleration