Sorry, i have problem in this question which comes from my textbook. I couldn't solve it and i would like someone to guide me. (Question) A body travels 30 metres in the sixth second of motion and 24 meters in the ninth second. Find: i) the initial velocity (ans: 41 m/s ) ii) the retardation, assumed uniform (ans: -2 m/s/s ) iii) the time elapsing before coming to rest (ans: 20.5s) From my thinking is that, the body is actually moving in a curve so it changes its displacement from 30 meters to 24 meters within the time [6~9] seconds, but this problem is in charge of kinetic problem as well, as it's in the chapter 'kinetic'. And since it's not moving in a straightline, i assume that it cannot apply the ordinary equation : S = u * t * 1/2 a*t^2; But by only reconstructing the equation from a = dv/dt; Plus, the retardation and initial velocity seems to be dependantly constant variable. So my guess is that, since it involves friction, i would simply guess that it's actually having altering of work as : Sum(W) = Fn * d(Sn); where W is the total Work, Fn is the changing of Forces within the time interval [0,t]; dSn is the delta of distance traveled within time interval [0,t]; Thanks in advance. Daniel.