1. The problem statement, all variables and given/known data A particle, mass m, moves along the path r = xi + yk where x = Rcos wt and y = Rsinwt where R and W are some constant. a)What sort of motion is this ? b)Find a vector expression for the velocity vector. c) Find a vector expression for the acceleration and hence by ( appropriate substitution) give its magnitude and direction in terms of, vector r. d) Write down the force vector, f. e) Show by evaluating the quantity F.v are perpendicular. f) Physically, what's the quantity F.v . 2. Relevant equations Dot rule : A.B = mag A . B . cos theta 3. The attempt at a solution Hi there, First of all I would like to mention that I appreciate any input which will be given on here. My attempt to the aforementioned set of problems has been as following: a) I said it's periodic or circular motion [ since w is present] b) For this part we know.. first derivative of vector r, is v. i.e dr/dt = v. so vector v = -wRsin(wt)+Rwcos(wt) c) This is the bit which I found out to be tricky and I may have made some wrong assumptions,mistakes. Acceleration vector = -w^2Rcos(wt)-w^2 Rsin(wt) Now from what I have understood is that they want me to get acceleration vector in the form of x's and y's , just as r = xi +yj ... Am I right ? If so.. by manipulation what I have got is : a = ( -w^2 xi - w^2 yj) I am lost beyond this... P.S: Sorry for my lack of latex notation since I am in a sort of rush to know about this problem.