what is the acceleration of a certain car if the velocity is constant?? is it zero?
The acceleration is the derivative of the velocity respect to time so if the velocity is constant, the acceleration would be 0 (m/s^2) (as the derivative of a constant is 0)
what's the meaning of derivative?
"the derivative is a measure of how a function changes as its input changes"
take a look in wiki: http://en.wikipedia.org/wiki/Derivative
Velocity is speed in a straight line. If the velocity is constant, there is no change in velocity, which is what acceleration is, so acceleration is 0 by definition. (Unless your teacher is very sneaky and is talking about the acceleration due to gravity.)
Derivatives are not necessary for this level of physics. Apparently you haven't had calculus, yet.
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