The characteristic that will be affected by increasing the speed of an object from 30 meters per second to 40 meters per second is kinetic energy.
Kinetic energy (KE) is given by the formula:
\[ KE = \frac{1}{2} mv^2 \]
where \( m \) is the mass of the object and \( v \) is its velocity. As the speed increases, the kinetic energy increases as well, since it is dependent on the square of the velocity.
So, the correct answer is kinetic energy.