damn!.... it took me a total of 30 minutes to solve this problem.... too much for an IITian. Anywayz.. i would like to give this question to you, if you solve it within 30 minutes you're Great! If within 45 minutes, you're just fit for an IIT entrance exam. just try it. question- a point object of mass m, moving in a circular path of radius "r" with a uniform speed v1 is at x at t=0. at the same time a man starts moving with uniform speed v2 along y-axis from origin . Find the linear momentum of the object with respect to the man as a function of time. note- here x is any point lying on the x-axis such that it is the point lying on the circle. here the circular path is inscribed between "x" and the origin and lies on x-axis. so you can count r= x/2.