According to the formula of KE.
KE = 1/2m • v^2.
Both of the variables of mass and energy m determines an object's kinetic energy. Assuming the mass of an object is held constant, the change in velocity, or velocity change will dictate the amount of kinetic energy that a particular object posses.
Isn't it a because in b at the start of the equation the E in Fe just disappeared
The given example is a chemical reaction.
The contents (separated as reactants and products) :

The written reaction is :

<em>I hope it helped you solve the problem.</em>
<em>Good luck on your studies!</em>