DE的motion问题求助

menglee

An object of m kg is given an upward velocity of 16m/s from rest, 16 m above the ground. Assume that the gravity is the only force acting on it, when will the object hit the ground and at what velocity will it hit the ground? (g=10 m/s^2)
我对那个velocity没有头绪，我能做到的是
m*dv/dt = ? - mg

问题没有类似v proportional to a 的东西，所以？不能是kv对吗？

puangenlun

以地面法线为轴
地上为正方向

s(0)=16 m
a=-10 m/s^2
v(0)=16 m/s

t时刻，物体着陆
d=v(0)t+(1/2)at^2
0=16*t+(1/2)(-10)*t^2
5*t^2-16*t=0
t(5*t-16)=0
t=0 or t=16/5

因为t>0, so t=16/5 s

v(t)=v(0)+at
   
v(16/5)=... ...

应该是这样做