The acceleration of a particle is inversely proportional to the square of the time since it was fired. If the acceleration of the particle 20 seconds after it was fired was 5 m/sec2, what was its acceleration 5 seconds later?
$$a=\frac{k}{t^2}\\\\ \mbox{ When } t=20\quad a=5m/s^2\quad \mbox{ Find k}\\\\ 5=\frac{k}{400}\\\\ k=2000\\\\ so\\\\ a=\frac{2000}{t^2}\\\\ When\quad t=25\\\\ a=\frac{2000}{25^2}\\\\ a=\frac{2000}{625}\\\\ accel=3.2m/s^2$$
