Homework Statement
A 4.50 ✕ 10^5 kg subway train is brought to a stop from a speed of 0.500 m/s in 0.900 m by a large spring bumper at the end of its track. What is the force constant k of the spring?
M- 4.50E5 kg
IV- .5m/s
FV- 0m/s
Homework Equations
k=mg/x
F=-kx
PE = (.5)kx^2The Attempt at...