A spring is compressed between two toy cars (m1 = 120 g, m2 = 180 g), which are placed on the floor and releas

Question

A spring is compressed between two toy cars (m1 = 120 g, m2 = 180 g), which are placed on the floor and released. It takes the spring 0.064 s to push the cars apart, after which they move directly away from each other, car 1 at a constant speed of 2.4 m/s.

(a) Calculate car 2’s speed after the spring is fully relaxed.
(b) Calculate the average force the spring exerted on car 1 while pushing the cars apart.

Answer 1

conservation of momentum applies to this example:
a) Since the cars were at rest and then moving
2.4*.120+v2*.180=0

solve for v2

b) you can use F=m*a where F is the average force
you know that at t=0.064 s v=2.4, so
2.4=a*0.064
compute a and plug into F=m*a to find F

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