Firstly, we note that the acceleration is constant, therefore this problem should be tackled with the SUVAT equations. Let's write down the information we have: s we are asked to find this u = 50 m/s v = 20 m/s a = -10 m/s2 (note that the plane is decelarating, hence the acceleration is negative!) t no information about time Let's write down the SUVAT equations, that we should know by heart: v = u + at s = ut + ½at2 s = ½(v + u)t v2 = u2 + 2as We have no information about t, therefore we will use the last equation. By inverting it we should come up with: s = 1/(2a) · (v2 - u2) = 1/(2 · (-10 m/s2)) · (400 m2/s2 - 2500 m2/s2) = 105 m In the end is always a good idea to make a couple sanity check: 1) Does the result have the correct unit of measurement --> Yes, meters is the unit of distance 2) Does the result seem intuitively reasonable? --> Yes We can now say we have solved the problem! :)