Kinetic energy, k = \(\frac{1}{2}\) mv2.
Where m = mass of the object
V = velocity of the object.
Here mass (m) is the same in both cases (∵ object is same)
\(\frac{k_1}{k_2}=(\frac{v_1}{v_2})^2\)
Initial kinetic energy k1 = 25J
Initial velocity V2 = 5 ms-1
New kinetic Energy K2 = ?
New velocity v2 = 3v1 = 3 × 5 = 10 ms-1
∴ When velocity is increased three times its K.E. is 225 J.