题目

A stone is dropped from a height h and falls the last half of its distance in 4s .what was the total time of fall

提问时间：2020-10-03

答案

we can use V to refer to the velocity when the stone falls the first half distance.
To the last half of its distance we can write the equation:V*T+(1/2)gT²=(1/2)h
In this equation ,T=4s,g=10m/s²
To the last half of its distance we can write two equation:(1/2)gT'²=(1/2)h
and g*T'=V
Use these three equation we can work out the T(all)=T+T'=4+4√2+4=8+4√2s