Apr 03, 2020 · If the particle moves forwards, then its velocity is positive, and if the particle moves backwards, then its velocity is negative. Velocity is obtained by differentiating its displacement, \( x \) in terms of \( t \). \( v = \displaystyle \dfrac{dx}{dt} \) or \( \displaystyle x = \int v dt \) Speed. Instantaneous speed is the magnitude of instantaneous velocity and is always positive, regardless of its direction either forwards or backwards. At Rest where [[alpha].sub.-max] is the preset negative acceleration limit, not necessarily equal to positive acceleration limit [a.sub.max]. Absolute adaptive CS model and modified strong tracking unscented filter for high maneuvering target tracking