\(a,v_0=18\left(\dfrac{km}{h}\right)=5\left(\dfrac{m}{s}\right)\\ v=54\left(\dfrac{km}{h}\right)=15\left(\dfrac{m}{s}\right)\\ Ta.có:v=v_0+a.t\\ \Leftrightarrow15=5+a.5\\ \Leftrightarrow a=2\left(\dfrac{m}{s^2}\right)\\ b,s=v_0t+\dfrac{at^2}{2}=5.5+\dfrac{2.5^2}{2}=50\left(m\right)\)