New to PF, so here it goes. Oh just a question, did this site use to have a dark skin? I can't remember if that was this or something else. 1. The problem statement, all variables and given/known data The position of a particle as a function of time (in s) is given by C1 + C2t + C3t2. Let C1 = 11.0 m, C2 = 9.5 m/s and C3 = -0.49 m/s2. What is the velocity of the particle at time t = 15.0 s? And what is the particle's acceleration at time t = 15.0 s? 2. Relevant equations Velocity is the derivative of position.(How do you make it look all nice?) Acceleration is the 2nd derivative of position. 3. The attempt at a solution Where do I start? I don't even understand the equation that's given. Judging from the question (it's online) it looks like those t are variables and not subscripts.