Was a little disappointed when at the end of the discussion on the everyday meaning of inertia ("things tend to remain at rest") vs the technical meaning ("things tend to remain at rest or in motion"), nobody offered the poor guy a substitute term without the ambiguity. The caller's son needs to develop, not inertia, but momentum.
OK, I just listened to that podcast. Totally agree with Ron. Momentum is a far better word to describe what the guy was asking about, and whether or not Grant knows that momentum = mv (and I suspect he does), it's a word that has entered common use in sports, politics, economics, etc. It was scientifically defined in Newton's Principia ca. late 17th century. But take a look at  this interesting result from Ngrams.
The rapid drop after 1800 is likely due to the fact that, by then, there wasn't much more to say about physical momentum. The gradual rise after that is certainly due to the term's incorporation as a metaphor for continued progress.
Note that my Ngram search was for "their momentum" in order to bias the results toward metaphorical uses. Physicists don't often speak of momentum collectively.
I may be wrong about this but the way I understand it, inertia of a specific mass never changes. Â It always has the same resistance whether it is resistance to move or resistance to stand still. Â Momentum changes. Â I have not heard the podcast with this but from the previous comments it sounds like the son needs momentum. Â That's what so many sons need.
Inertia is a function of mass only. Â Momentum, on the other hand, is a function of both mass and vector. When pool balls collide, their inertia does not change, but their momentum certainly does.
Within the confines of Newtonian physics, of course. Â
There is no ambiguity. Â Both the gas pedal and the brake pedal work to defeat inertia.
Momentum is what you already have: politicos , athletes ride on the momentum from the last victory.
To develop momentum, you first need energy from external source: a victory, getting hit by another pool ball, a kick in the pants.
Inertia in the real world actually matches the technical sense just fine: You sit around not wanting to do anything, or do the same job day in day out wishing no advancement. (In the first case you have no momentum, in the 2nd you have some momentum handy in case a better job comes along.)