Question

物理······高一必修一·····

Answer 1

关键是熟练运用方程或方程组解题.

VC-VB=at

-VB=at

a=-VB/t=-VB/0.5=-2VB

VB^2-VA^2=2as

VB^2-4VB^2=-4VB*0.75

VB=1m/s

a=-2m/s^-2

VB-VD=at

1-4=-2t

t=1.5s