懂英文的进.A light is at the top of a pole 80ft high.A ball is dropped at the same height from a point 20ft from the light.Assuming that the ball falls according to the law s=16t^2,how fast is the shadow of the ball moving along the ground one s

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懂英文的进.A light is at the top of a pole 80ft high.A ball is dropped at the same height from a point 20ft from the light.Assuming that the ball falls according to the law s=16t^2,how fast is the shadow of the ball moving along the ground one s

懂英文的进.A light is at the top of a pole 80ft high.A ball is dropped at the same height from a point 20ft from the light.Assuming that the ball falls according to the law s=16t^2,how fast is the shadow of the ball moving along the ground one s
懂英文的进.
A light is at the top of a pole 80ft high.A ball is dropped at the same height from a point 20ft from the light.Assuming that the ball falls according to the law s=16t^2,how fast is the shadow of the ball moving along the ground one second later?
答案是200ft/sec.

懂英文的进.A light is at the top of a pole 80ft high.A ball is dropped at the same height from a point 20ft from the light.Assuming that the ball falls according to the law s=16t^2,how fast is the shadow of the ball moving along the ground one s
XXV2008 ,
中文意思如下：灯在一个高80英尺的竿的顶端,一个在竖直位置与灯同高,水平方向距灯20英尺的点落下,假定灯以s=16t^2（s为距离,t为下落时间）的规律下落,请问,1秒后灯的影子沿地面移动的速度是多少?
楼主,你画一个图,最重要的关系就是下落的过程中,始终有两个三角形相似,你利用这个关系,然后微分一次求出加速度,也就等价的求出了速度.

球下落一秒后v=ds/dt v=32ft/sec
这是竖直方向分量 水平方向为v‘=40ft/sec
16:80=1:5
影子的速度v"=v'*5=200ft/sec
这是最终不考虑影子速度方向的结果下

懂英文的进.A light is at the top of a pole 80ft high.A ball is dropped at the same height from a point 20ft from the light.Assuming that the ball falls according to the law s=16t^2,how fast is the shadow of the ball moving along the ground one s Look at the sun!How _____ it is!A.bright B.brightly C.light D.lightlybright 和light 的区别 及四个选项的词性 there is a light ahead.是不是there is a light that is ahead的省略? 灯的英文light We should stop at a red light.的问句是什么? We should stop at a red light.的问句? Slow down and stop at a yellow light.的意思 填入适当的单词,使句意完整.1.（ ）at a red light.2.( )at a green light. stop at a erd light这句英文怎么读中文叫什么 light travels at a speed which is about a million times faster than that of sound.a million times faster是一百万倍的速度吗?举例 Look at the sun.How__it is!A.brigh B.brithtly C.light D.lightly求解释 this is a long light. there is a light 歌词 love is a light that never dims.谁写的 分别翻译:stop at a red light和wait at a yellow light与go at a green light. 括号里应该填什么单词?（ ）at a red light ( ) at a yellow light ( ) at a green light a yellow wait at light 怎么连 ________________?We stop at a red light.