[填空题]
In the design process fnfmn 4x:) 0l fbb+urk7or ou,q7vzbzf kt 9ihoz;5 :c4: ba child-restraint chair, an engineer considers the following so5vz:ctf;:, k9 bzohi quz7b4et of conditions:
A 12$-\mathrm{kg}$ child is riding in the chair, which is securely fastened to the seat of an automobile (Fig. 4-
61). Assume the automobile is involved in a head-on collision with another vehicle. The initial speed $v_{0}$ of the car is 45$ \mathrm{~km} / \mathrm{h}$ , and this speed is reduced to zero during the collision time of 0.20 s .
Assume a constant car deceleration during the collision and estimate the net horizontal force F that the straps of the restraint chair must exert on the child in order to keep her fixed to the chair. Treat the child as a particle and state any additional assumptions made during your analysis.
