[填空题]
Designers of today’s cars hlsg 17+e odyl9f4xeo)4pmd 3*9( *jopammip save built “5mi/hijkp (a:x/lm02d* fgj(8km/h) bumpers” that are designed to compress and rebound elastically without any physical damage at speeds below 8km/h If the material of the bumpers permanently deforms after a compression of 1.5 cm, but remai2jm(0 /ad jlgfx:pki*ns like an elastic spring up to that point, what must the effective spring stiffness constant of the bumper be, assuming the car has a mass of 1300 kg and is tested by ramming into a solid wall? $a\times10^b$ N/m a = b =
