A train of mass 1600 kg attains a speed of 25 ms\(^{-1}\) in 20 seconds….

Explanation

where force = f, mass = m, acceleration = a, velocity = v, time = t

Force = m * a → m * \(\frac{Δv}{t}\) 

Power = f * v

P = m * \(\frac{v}{t}\)  * v = m * \(\frac{v^2}{t}\) 

p =  \(\frac{1600 * 25^2}{20}\) 

p = 50,000 or 50 KW

There is an explanation video available .