A mass m is projected vertically upwards at t = 0 from y = 0 with initial velocity v0 > 0 along the y-axis. (+y is upwards) The mass moves under the constant force of gravity, and also a force of air resistance with magnitude given by cv^2 . Derive the velocity v of the mass as a function of position y in its upward motion, and also find the position at which the mass is instantaneously at rest.