The backrest of the chair is to be spring loaded to permit chair to recline slightly. Design specifications call for deflection of not more that two inches when the 150 lb person lean 40% of his or her body weight on backrest(suppose that there are no lever arm between backrest and spring to account for problem)
i) Utilize Newton's law to find force applied to backrest when 150-lb person leans 40% of his or her body weight it.
ii) Find constant requiered for spring.
c) If the 200 lb person puts 70% of his or her body weight on backrest, what spring extention would be expected? Suppose that applied force is still within allowable limits for spring.