[填空题]
Designers of today’s cars have b* do-plflt1s98jt k2j 5 hb+pxuilt “5mi/h(8km/h) bumpers” that are designeduj(obtp9p:2 a5h zewlwu4.g5t3- 3bzqrq 9lw 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 remains j . tl5q:wlb ogz3awer(qw9tbuppz h-2953u 4like 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 =
