Re: [問題]
※ 引述《Jiadar (暮然回首燈火闌珊)》之銘言：
: ※ 引述《Jiadar (暮然回首燈火闌珊)》之銘言：
: : a football kicker can give the ball an initial speed of 25 m/s.
: : within what two elevation angles must he kick the ball to score a
: : field goal from a point 50 m in front of goalposts whose horizontal
: : bar is 3.44 m above the ground ?(if you want to work this out algebraically
: : ,use sin平方+cos平方=1 to get a relation between tan平方 and 1/cos平方,
: : subsitute,and then solve the resulting quadratic equation)
: ┌────┐─ ●
: │ │↑ v = 25 m/s ╲｜╱
: │ │↓ 3.44 m ↖ ｜
: └────┘─ Θ ● ／＼
: ∣←───50 m───→∣
: 如果要把球踢進
: Θ的範圍在幾度之間?
X=Vcosθ×T=50 =>T=50/(Vcosθ)代入下式
Y=Vsinθ×T-(1/2)gT*2
=Vsinθ×50/(Vcosθ)-(1/2)g[50/(Vcosθ)]*2
=50tanθ-(1250g)/(Vcosθ)*2
=50tanθ-(1250g/V*2)(1+tanθ*2)<3.44
這樣應該可以解ㄌ吧
我懶的解ㄌ
ㄎㄎㄎ.....:P
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