Solve this:
Velocity and acceleration of a particle at some instant of time are $\overrightarrow{v}=(3\hat{i}+4\hat{j}) m/s and \overrightarrow{a}=(6\hat{i}+8\hat{j}) m/s^2$ respectively. At the same instant particle is at origin. Maximum x-co-ordinate of particle is K/4 then the value of K will be 

A particle is projected from point O on the ground with velocity $u=5\sqrt{5} m/s$ at angle $\alpha ={\tan }^{-1}(0.5).$ It strikes at a point C on a fixed smooth plane AB having inclination of 37^o with horizontal. If the particle does not rebound, find the x-coordinate of point C in reference to co-ordinate system as shown in the figure. (g = 10 m/s)