this is all about understanding experimental data we will make extensive use of plotting to visualize the dataand will return to the topic of what is and what is not valid statistical conclusion we will also talk about the interplay between physical and computational experiments the behavior of springs springs are wonderful things when they are compressed or stretched by some forcethey store energy when that force is no longer applied they release the stored energy this property allows them to smooth the ride in carshelp mattresses conform to our bodiesretract seat beltsand launch projectiles in the british physicist robert hooke formulated hooke' law of elasticityut tensiosic visin englishf -kx in other wordsthe forcefstored in spring is linearly related to the distancexthe spring has been compressed (or stretched(the minus sign indicates that the force exerted by the spring is in the opposite direction of the displacement hooke' law holds for wide variety of materials and systemsincluding many biological systems of courseit does not hold for an arbitrarily large force all springs have an elastic limitbeyond which the law fails those of you who have stretched slinky too far know this all too well the constant of proportionalitykis called the spring constant if the spring is stiff (like the ones in the suspension of car or the limbs of an archer' bow) is large if the spring is weaklike the spring in ballpoint penk is small knowing the spring constant of particular spring can be matter of some import the calibrations of both simple scales and atomic force microscopes depend upon knowing the spring constants of components the mechanical behavior of strand of dna is related to the force required to compress it the force with which bow launches an arrow is determined by the spring constant of its limbs and so on