EES 0836 Lecture 29: Lecture 29
3 Apr 2016
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K is the spring constant in newtons per meter (n/m) The negative sign means opposite to the direction of displacement: example, if the springs in your 1000 kg car compress by 10 cm (e. g. , when lowered off of jacks): Then the springs must be exerting mg = 10,000 newtons of force to support the car. F = kx = 10,000 n, x = 0. 1 m. 4,000 = (100,000) x, so (cid:1)x = 4/100 = 0. 04 m = 4 cm: could have taken short-cut: Springs are linear, so 400 additional kg will depress car an additional 40% (400/1000) of its initial depression: energy storage in spring, applied force is k(cid:2)x (reaction from spring is (cid:1)k(cid:2)x) Starts at zero when (cid:2)x = 0. Slowly ramps up as you push: work is force times distance, let"s say we want to move spring a total distance of x would naively think w = k x2.
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