Physics helpp please!
posted by Kate .
A 8000kg freight car rolls along rails with negligible friction. The car is brought to rest by a combination of two coiled springs as illustrated in the figure below. Both springs are described by Hooke's law and have spring constants with k1 = 1700 N/m and k2 = 3700 N/m. After the first spring compresses a distance of 29.4 cm, the second spring acts with the first to increase the force as additional compression occurs as shown in the graph. The car comes to rest 45.0 cm after first contacting the twospring system. Find the car's initial speed.

if the springs are in series then the combined spring constant is 1/k=1/1700 + 1/3700
k= (1700*3700)/5400=1168N/m
1/2 k x^2=1/2 m v^2
you have k, x (.45m), and mass m. Solve for v 
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