Which would have a greater effect on the kinetic energy of an object: doubling the mass,or doubling the velocity?

$A$ boy of mass $40 \, kg$ runs up a flight of $50$ steps,each $10 \, cm$ high,in $5 \, s$. Find: $(i)$ the work done by the boy,and $(ii)$ the power developed. $(g = 9.8 \, m s^{-2})$

Calculate the kinetic energy of a car of mass $750 \,kg$ moving with a velocity of $54 \,km \cdot h^{-1}$. Find the new kinetic energy of the car if a passenger of mass $50 \,kg$ sits in the car.

$(a)$ Derive an expression for the kinetic energy of a body having mass $m$ and moving with a velocity $v$.
$(b)$ When the velocity of a body is increased $5$ times,what is the change in its kinetic energy?
$(c)$ Two masses $m$ and $2m$ are dropped from heights $h$ and $2h$. On reaching the ground,which will have greater kinetic energy and why?

$A$ man drops a $10\, kg$ rock from the top of a $5\, m$ ladder. What is its kinetic energy when it reaches the ground? What is its speed just before it hits the ground?

$A$ light and a heavy object have the same momentum. Find the ratio of their kinetic energies. Which one has a larger kinetic energy?