-一物体从斜面顶端由静止开始做匀加速运动下滑到斜面底端
1个回答

设总时间为t

s2-s1=1.2m

s1:s2=3:7

s1=0.9m

s2=2.1m

则:s1=1/2a*3^2=0.9m

a=0.2m/s^2

s2=1/2a*t^2-1/2a*(t-3)^2=2.1m

t=5s

斜面长度L=1/2at^2=1/2*0.2*5^2=2.5m