A2.0-kg mass and a 3.0-kg mass are on a horizontal frictionless surface, connected by a massless spring with spring constant k = 140 n/m. a 15-n force is applied to the larger mass, as shown in fig. 4.23. how much does the spring stretch from its equilibrium length?

The solution would be like this for this specific problem:

=> F/2 = (15 - F)/3 
=> 3F = 30 - 2F 
=> 5F = 30 
=> F = 6 N 

So if the spring stretches by x, 
F = kx 
=> x = F/k = 6 / 140 m = 600 / 140 cm = 4.3 cm

The spring stretches for 4.3 cm.

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