Where does buoyancy collide?

The upward force a fluid exerts on any object placed in it, equal to the weight of the fluid the object pushes aside: this is Archimedes' principle, and it is what makes a boat float, a balloon rise, or a stone feel lighter under water. Graf's 2004 Just What Did Archimedes Say About Buoyancy? revisits the original statement and shows how the upward force follows from the pressure of the surrounding fluid increasing with depth. Here buoyancy is a static mechanical force measured in newtons, fixed by the fluid's density and the volume displaced, and it is not a market's rising tone, a student's bounce-back from a bad grade, or the stored energy that lifts an air parcel, though that last meaning grows from the same physics.[1]

Unit

The upward force on a body in a fluid, in newtons

Recovery means

Not applicable

Measured by

Computed as fluid density times displaced volume times gravity, or found by weighing the object in and out of the fluid

In the atmosphere, buoyancy is the net upward acceleration on a parcel of air that is warmer, and so less dense, than the air around it, and it is the driver of convection, cumulus growth, and thunderstorms. Meteorologists add up this parcel buoyancy over the depth through which a rising parcel stays warmer than its surroundings to get CAPE, the convective available potential energy, a measure of how much energy a storm can draw on. Doswell and Rasmussen's 1994 The Effect of Neglecting the Virtual Temperature Correction on CAPE Calculations shows how sensitive this integrated buoyancy is to how the parcel's temperature is defined. Although it rests on the same density physics as the force on a submerged body, here buoyancy is an acceleration gathered into an energy per unit mass, and it has nothing to do with a buoyant tax base or a student's academic resilience.[2]

Unit

A parcel's upward acceleration, integrated as CAPE in joules per kilogram

Recovery means

A rising parcel loses its buoyancy at the level where its density matches the surrounding air, which caps the convection

Measured by

Computed from an atmospheric sounding as the vertically integrated positive buoyancy of a lifted parcel

In public finance, tax buoyancy measures how strongly a country's tax revenue responds to growth in its economy: a buoyancy of one means revenue rises in step with GDP, while a figure above one means revenue grows faster than output, counting both the automatic effect of a wider tax base and any deliberate changes to rates or rules. Dudine and Jalles's 2018 How Buoyant Is the Tax System? estimates these responses across a large panel of countries and separates the short-run reaction from the long-run one. Here buoyancy is a dimensionless ratio of revenue growth to output growth, a property of a fiscal system, and it shares nothing with the force on a floating object, the lift inside a storm cloud, or a student's recovery from a bad week, beyond the image of something staying up.[3]

Unit

A dimensionless ratio: the percentage change in tax revenue per one percent change in GDP

Recovery means

Not applicable

Measured by

Estimated by regressing changes in tax revenue on changes in GDP, over both the short run and the long run

In educational psychology, academic buoyancy is a student's capacity to deal well with the ordinary setbacks and pressures of school, a poor grade, a hard deadline, a patch of low confidence, rather than the chronic, severe adversity that the related idea of resilience addresses. Martin and Marsh's 2008 Academic buoyancy: Towards an understanding of students' everyday academic resilience introduced the construct and set this everyday coping apart from major resilience, linking it to factors like confidence, composure, and persistence. Here buoyancy is a personal disposition measured by self-report survey, a trait of a learner, and it has no connection to the force on a submerged body, the energy that drives a storm, or the responsiveness of tax revenue to growth.[4]

Unit

A person's everyday academic coping capacity, as a self-report score

Recovery means

The construct is itself about recovering from routine academic setbacks

Measured by

Assessed by self-report scales such as the Academic Buoyancy Scale