Given, \\\\(velocity \\: of \\: object, v = 5 \\:ms^{-1}\\\\);\\\\(kinetic \\: energy \\: of \\: an \\: object, \\: E_K= 25 \\: J\\\\)\\\\(\\displaystyle E_K=\\frac{1}{2}mv^2\\\\) or \\\\(\\displaystyle 25=\\frac{1}{2}\ imes m \ imes (5)^2\\\\)or \\\\(\\displaystyle m =\\frac{50}{25} = 2 \\: kg \\\\)When the velocity triples,\\\\(\\displaystyle E_K=\\frac{1}{2}mv^2=\\frac{1}{2}\ imes 2 \ imes (15)^2= 225 \\: J\\\\)