Question

一只小球自屋檐自由下落，在Δt=0.25 s内通过高度为Δh=2 m的窗口，求窗口的顶端距屋檐多高.（取g=10 m/s²）

Answer 1

思路解析：设窗顶离屋檐距离为h，球落到窗顶处的速度为v₁，落到窗底处的速度为v₂，则

v₁=gt₁                                                                        ①

v₂=g (t₁+Δt)                                                                  ②

v₂²-v₁²=2g·Δh                                                               ③

将①②两式代入③得：g²(t₁+Δt)²-g²t₁²=2g·Δh，代入数据得t₁=0.675 s

所以h=gt₁²=×10×0.675² m=2.28 m.

答案：2.28 m