# physics

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A 5.00×105-kg subway train is brought to a stop from a speed of
0.500 m/s in 0.400 m by a large spring bumper at the end of its track.
What is the force constant k of the spring?

• physics -

KE=PE
mv²/ 2 =kx²/2
k=m(v/x) ²

• physics -

mvi^2=kxf
k=mvi^2 / xf2
k=(5.00*105)(0.5)^2 / (0.4)
k=328 N/m

• physics -

oops, forgot to square my x

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