How could you increase the kinetic energy of a truck without increasing its velocity?

Kinetic energy consists of 2 elements, mass and speed. If its velocity, that is speed, remains the same, you have to increase the mass to increase its kinetic energy without affecting velocity.

Kinetic energy of something depends on its mass and speed. 
So if you want to keep the same speed but increase its kinetic
energy, then the simple answer is that you have to increase the mass.

But it's not as simple as that.

If there's a truck cruising along the highway, and you want to increase
its kinetic energy without changing the speed, then it's true ... you'll
have to increase the mass.  You might have a helicopter swoop in low
over the truck and drop some bales of hay onto it.  That will certainly
increase the mass. But that DOESN't magically increase the kinetic
energy.  More energy has to COME from somewhere.

When the bales hit the bed of the truck and the mass suddenly increases,
if the driver doesn't want his speed to drop, he has to mash the gas pedal
a little farther, run the engine a little faster, and let the engine deliver more
energy.  THAT's where the extra kinetic energy comes from ... extracting
more chemical energy out of more gasoline.

Is a  vector quantity  that refers to "the rate at which an object changes its position." imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. while this might result in a frenzy of activity, it would result in a zero velocity. because the person always returns to the original position, the motion would never result in a change in position. since velocity is defined as the rate at which the position changes, this motion results in zero velocity. if a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. every step must go into moving that person further from where he or she started. for certain, the person should never change directions and begin to return to the starting position.