题目

第一个问已经做出来,求第二问最好带过程,
If a ball is thrown vertically upward from the roof of a 32 foot tall building with a velocity of 112 ft/sec,its height in feet after t seconds is s(t) = 32 + 112 t - 16 t^2.What is the maximum height the ball reaches?（228）
What is the velocity of the ball when it hits the ground (height 0)求第二问过程

提问时间：2021-01-13

答案

因s(t) = 32 + 112 t - 16 t^2 = 228 - 16*(t-7/2)^2所以当t=7/2时,达到最大值228因速度v(t)=V0 + a * t = 112 + a* 7/2 = 0,所以加速度a = -32又因落地时s(t) = 0,所以t = (7+根号57)/2落地时v(t) = 112 - 32 * (7+...