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some spcial vehicles have spinning disks to store energy whil they roll downhill. they use that stored energy to lift themselves uphill late on. their flywheels have relatively small rotational masses but spin at enormous angular sppes. how would a flywheel's kinetic energy change if its rational mass were FIVE times larger bit its angular speed were FIVE times smaller?

2007-09-25 05:19:53 · 2 answers · asked by sippy85 1 in Science & Mathematics Physics

2 answers

A flywheel has a moment of inertia
I=.5*m*r^2

and kinetic energy of
.5*I*w^2

so
KE=m*r^2*w^2/4

the mass is linear while the speed is exponential.

Plug in the numbers
KE(5)/KE(1)=5/25=1/5

j

2007-09-25 05:26:40 · answer #1 · answered by odu83 7 · 0 0

The kinetic energy of a rotating flywheel is

E = ½ I ω²

where I is the moment of inertia and ω is the ngular velocity. Assuming (not a bad assumption) that I is proportionial to the mass when the mass is changed, then for the new system,

E(new) = ½ (5*I) (ω/5)² = E(original) / 5

2007-09-25 05:28:36 · answer #2 · answered by anobium625 6 · 0 0

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