yeah... but it's more like a law of math than it is of physics....
a drop in a cup is more significant than a drop in a bucket which is more significant than a drop in the sea.
and it's always easier to drop your avg speed than it is to increase it. the closer your average gets to your max cruising speed, the harder and harder it is to maintain that average.... your average asymptotically approaches your max speed.
that's why it's easier for a 3.3 GPA student to improve to a 3.4 than it is for a 3.8 GPA student to improve to a 3.9.