A particle P of mass 0.4 kg is moving under the action of a constant force F newtons. Initially the velocity of P is (6i – 27j) m s−1 and 4 s later the velocity of P is (−14i + 21j) m s−1 . Find, in terms of i and j, the acceleration of P.

On the whiteboard I would provide a brief drawing of the particle, and of all the information provided (force applied to P and its before and after velocity) as a visual aid for the student. I would ask/remind the student of the equation for acceleration (= (final velocity - initial velocity)/time), and then prompt them to use the information provided in the question to find values to substitute into the equation. From this we would get acceleration = ((-14i + 21j) - (6i - 27j))/4Step by step I would encourage the student to simplify the equation to make it more manageable i.e. (-14i + 21j - 6i + 27j)/4Then (-20i + 48j)/4From this we can finally reach the answer - 5i + 12j