计算或测量了力的大小后，你可以得出两个力的合力。下面我们教你怎么做。
步骤
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1
画出想要计算合力的力，标出力的大小。
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2
决定一个正方向（比如右或上）。反方向的力前面要加负号（如左或下）。
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3
将各个方向的力用+或-标出来。
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4
将所有的大小加起来。同向力数值相加，反向力数值相减。最后得到两个力的合力。
方法 1 的 1:
计算斜力
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1
如果有斜向的力，即以一定角度给物体施加作用的力，需要找出水平分力(Fx) 和竖直分力(Fy)，来找出它的大小。这里要用到三角函数，以及方向角 (一般是 θ， "theta")。方向角 θ 总是从x正半轴开始测量。
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2
使用三个基本的三角比率，将斜力作为一个直角三角形的斜边，直角边是Fx、Fy。因此：
- Fx = cos θ * F
- Fy = sin θ * F
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3
注意，可能会有多个斜力同时作用在一个物体上，所以要找出他们的Fx和Fy。然后在Fx方向合并，Fy方向也合并，得到最后的水平和竖直方向的合力。
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4把最终两个方向的合力代入计算斜向合力的公式： sqrt((Fx_total)2 + (Fy_total)2)