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?

Step-by-step solution Step 1 of 1 The sum of the change in potential energy of the spring and change in kinetic energy of the train is equal to zero since the train brought to stop by the spring, Or, The change in the potential energy of the spring is The change in the kinetic energy of the train is Since, Therefore, Or Substitute for , for , and for in the above equation. Hence, the force constant k of the spring is .