If the length of a #21 cm# spring increases to #36 cm# when a #8 kg# weight is hanging from it, what is the spring's constant? Physics Forces and Newton's Laws Newton's Third Law 1 Answer ali ergin May 17, 2016 #K=523.2 " "N/m# Explanation: #Delta x=36-21=15 cm=0.15 m# #G=m*g=8*9.81=78.48N" Force which it stretches the spring"# #F=-K*Delta x " the sign '-' shows direction"# #F:"force which it calls back"# #K:"Spring constant"# #-F=G# #78.48=K*0.15# #K=(78.48)/(0.15)# #K=523.2 " "N/m# Answer link Related questions How does Newton's third law apply to baseball? How does Newton's third law apply to soccer? How does Newton's third law apply to roller coasters? How does Newton's third law apply to gravitational force? How does Newton's third law apply to a mousetrap? Does the conservation of momentum really imply Newton's third law? How does Newton's third law apply to a rifle firing a bullet? How do action-reaction pairs keep a book sitting on a table in equilibrium? Do action and reaction pairs of forces balance one another? Do action and reaction pairs cancel one another? See all questions in Newton's Third Law Impact of this question 1880 views around the world You can reuse this answer Creative Commons License