In kynematics you describe the motion of particles using vectors and their change in time. You define a position vector r for a particle, and then define velocity v and acceleration a as


In dynamics Newton's laws predict the acceleration for a given force. Knowing the acceleration, and the kynematical relations defines above, you can solve for the position as a function of time: r(t)
Answer:
Kinetic energy of bigger rock will be more than that of smaller one.
Explanation:
Kinetic energy of the rock is given by,
Kinetic energy = 
As velocity of both the rocks are same. Thus, kinetic energy is directly proportional to the mass of the rock
Kinetic energy ∝ mass
So, For greater mass kinetic energy will be greater and for smaller mass kinetic energy will be smaller.
Hence, Kinetic energy of bigger rock will be more than that of smaller one.
When you are talking about calculating the kinetic energy of an object, the formula is as stated:
Ek =1/2mv²
Where m is mass and v is velocity. Sub all those numbers in and you'll get 25J of kinetic energy.
I’m pretty sure it’s lean mass but let another guy answer you before you use mine