我想問下 2003 CE Physics MC 第8題

圖片參考：http://hk.geocities.com/viceleader982040/itshouldccc.jpg



When the car accelerates at 3ms^-2 ,the child acclerates at 3ms^-2 as well.The net force acting on the child in the horizontal direction is F=10x3=30.Also,the car exerted a force ,which is the normal reaction(100N),on the child.So the force exerted by the safety seat on the child should be the resultant force of the noraml reaction and the force F,i.e.√30^2+100^2=104N//

首先有兩個力作用在child上...一是椅背對child的正交力...
二是椅面對child的法向反作用力......
椅背是3*10...椅面是10*10...
再計算合力...30^2十100^2=合力^2...
便可計算到c.........