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- Thread starter AnthroMecha
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- #2

cepheid

Staff Emeritus

Science Advisor

Gold Member

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First of all,

Second of all, use the mnemonic

Third of all, realize that in decomposing force vectors, there are usually only ever

Code:

```
|\
| \
| \
| \
| \
Fy | \ F
| \
| \
| \
| \
| <------ θ
|_______\
Fx
```

sinθ = F

cosθ = F

F_{y} = Fsinθ

F_{x} = Fcosθ

F

Code:

```
|\
| \
| <------ θ
| \
| \
Fy | \ F
| \
| \
| \
| \
| \
|_______\
Fx
```

sinθ = F

cosθ = F

F_{y} = Fcosθ

F_{x} = Fsinθ

F

So, you can see that, if the angle is measured from the horizontal, then the cosine is associated with the horizontal component, and the sine is associated with the vertical component.

if the angle is measured from the vertical, then the cosine is associated with the vertical component, and the sine is associated with the horizontal component.

- #3

tiny-tim

Science Advisor

Homework Helper

- 25,832

- 251

I keep telling people …What is an easy way of remembering which function to use to find the force in the direction of x and force in the direction of y?

It's

whenever it

maybe θ is marked on the diagram, but if the angle you

(however, a good *check* , when you're using *slopes*, is to imagine "what would happen if the slope was 0°?" … would the component *vanish* (sin0°) or be a maximum (cos0°) ?)

- #4

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This forum always delivers. Thanks guys these are very useful tools.

- #5

SammyS

Staff Emeritus

Science Advisor

Homework Helper

Gold Member

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SohCahToa !

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