The distance travelled in `'t'` second s by an object starting with a speed of u metres/second and moving along a straight line with speed Increasing at the rates of a metres/second every second is given by `ut+1/2 at^2` metres. An object moving in this manner travels 10 metres in 2 seconds and 28 metres in 4 seconds with what speed did it start? At what rate close its speed change?