Anh khong nho ly lop 10 lam nhung dai loai the nay nheGia toc $a=\frac{v-v_{o}}{t}=\frac{20}{t}$ (1) Voi t la thoi gian di quang duong 1km de tang van toc do'.
Quang duong di dk $s=v_{o}t+\frac{at^{2}}{2}<=> the cai (1) vao dk 1= 40t+\frac{20t}{2}$
Tinh dk ngay $t=0.02h$ thay vao (1) dk $a=1000km/h^{2}$
^^