The
disc on a 4 1/2" angle grinder spins at less than half this speed.
Centripetal force is the force that pulls inwards on a rotating object,
like when you turn round and round in a circle, holding a rope with a
weight on the end and the weight flies outwards. In that scenario, you
can feel the tension in the rope. That's the reaction to you pulling
inwards (Newton's third law - "For every action there is an equal and
opposite reaction"). For a rope or angle grinder disc, the material can
withstand the tension and grinder disks are reinforced with nylon mesh
to stop them exploding. In the case of a spinning neutron star reported in the article, the
immense gravity is the force that prevents it flying apart.
