Since you use the term "drag coefficient" can we assume that you know what it means? According to Wikipedia, the drag coefficient is given by \(\displaystyle c_d= \frac{2F_d}{\rho u^2A}\) where \(\displaystyle c_d\) is the drag coefficient, \(\displaystyle F_d\) is the drag force, \(\displaystyle \rho\) is the density of the fluid, u is the speed through the fluid, and A is the cross section area. You are asked for the drag force so solve for that: \(\displaystyle F_d= \frac{c_d\rho u^2A}{2}\). You are given that A= 400 square cm. and \(\displaystyle c_d= 0.6\). You will need to look up the density of air and water and calculate u, the speed of an object moving at 1000 rev/min around a circle of radius \(\displaystyle 10 sin(120^o)\).