Streaklines are traced out by neutrally buoyant marker fluid injected into a flow field from a fixed point in space. A particle of the marker fluid that is at point ðx, yÞ at time t must have passed through the injection point ðx0,y0Þ at some earlier instant t =τ. The time history of a marker particle may be found by solving the pathline equations for the initial conditions that x=x0, y=y0 when t =τ. The present locations of particles on the streakline are obtained by setting τ equal to values in the range 0≤τ ≤t. Consider the flow field V! =axð1+btÞ^i+cy^j, where a=c=1 s−1 and b=0:2 s−1. Coordinates are measured in meters. Plot the streakline that passes through the initial point ðx0,y0Þ=ð1,1Þ, during the interval from t =0 to t =3 s. Compare with the streamline plotted through the same point at the instants t =0, 1, and 2 s.