Just as Davidís experimental hammer hangs in gravitational balance provided the equilibrium is precisely maintained, so Arzhang Pezhmanís Gravity explores the fragile balance in teacher-student relationships and mental health.
Premiering last month, The Birmingham Repertory Theatre Company is now touring with acclaimed Pezhmanís chilling glimpse of life in the typical secondary school Ė something he knows well as a teacher himself.
David (vulnerably played by Nigel Hastings, last in the region with Journeys End) is passionate about physics.
The Large Hadron Collider is about to push the envelope of science or punch a black hole in the planet, and his enthusiasm is infectious. Which is just as well as trying to teach the disinterested, disaffected likes of Reece and Chantay is soul-destroying but his return from depression-related sick leave is a welcome change for the pupils compared with the bumbling supply teachers who have filled the void.
That is short-lived Ė even emotionally needy loner Kyle (a compelling performance by Ashley Hunter) who is a bright spark among the dross crosses the line to drop-out subscribing to yoof mentality rather than remain viciously bullied by the brutal likes of yob Reece (a superbly believable creation by Boris Mitkov).
Imogen Slaughter is the schoolís pastoral care worker Kathy struggling to find ways of balancing the needs of the school, the disruptive influence of recalcitrant 15-year-olds, the mental health of teachers and the looming OFSTED inspection.
But in a system where hoodlums just cannot be controlled and are sent off to abseil during school hours in a bid to curtail their disruptive conduct while blossoming talent is rewarded with computer-printed certificates, the balance is all too delicate and elements collide with explosive results.
Rebecca Loudon ably completes the cast as lacklustre, chavvy Chantay welded to her phone and Reece but with a back story concerning a brother stationed in Afghanistan - a mostly unexplored seam in a tale which tries to deal with (perhaps too) many issues in a fast 90 minutes.
Fabrice Serafinoís slickly adaptable set moves the action from science lab to playground to office seamlessly giving little welcome relief from the building tension while Edward Lewisís chosen sound track of contemporary music places this firmly in 2010.
An interesting piece but donít let student teachers in.