What is the particle's velocity v of t at t is equal to two? So pause this video, see if you can figure that out. Well, the key thing to realize is that your velocity is a function of time, is the derivative of position, and so this is going to be equal to, we just take the derivative with respect to t up here. So derivative of t to the third with respect to t is three t squared. If that's unfamiliar, I encourage you to review the power rule. The derivative of negative four t squared with respect to t is negative eight t, and derivative of three t with respect to t is plus three. Derivative of a constant doesn't change with respect to time, so that's just zero.