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](/uploads/image/z/8884857-57-7.jpg?t=%E6%87%82%E8%8B%B1%E6%96%87%E7%9A%84%E8%BF%9B.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%3D16t%5E2%2Chow+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