# What is the spring stiffness?

by ohheytai
Tags: spring, stiffness
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 P: 85 In outer space a rock of mass 4 kg is attached to a long spring and swung at constant speed in a circle of radius 6 m. The spring exerts a force of constant magnitude 720 N. What is the speed of the rock? i found the speed it is 32.8 m/s part 2: The relaxed length of the spring is 5.7 m. What is the stiffness of this spring? thats what i have no idea about could someone help lead me in the direction of solving it or show me how? please and thanks! 2. Relevant equations i used F=mv^2/r to get speed
 P: 709 Hooke's law: F=-Kx x is the change in length of the spring due to a force F. K is the the spring constant or "stiffness"
 P: 85 thanks!
 P: 709 What is the spring stiffness? what are you talking about it changes from 6m to 5.7m, there is no material in the world with no elasticity.

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