- #1

unscientific

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## Homework Statement

Here I have drawn for the following scenarios:

__Linear Resistance F__

_{R}= -k[itex]\vec{v}[/itex]a)Free-fall starting from rest, downwards as positive.

Now it gets trickier...

b)Free-fall starting from rest, upwards as positive.

My reasoning is as such:

Since the resistive force always points opposite to the velocity vector, in this case the velocity is

**pointing downwards**since the object is moving downwards:

**v**= -v

**i**. Hence F = -b

**v**= bv

**i**

The force points upwards.

__Quadratic Resistance__

F = -bv

^{2}

**i**or bv

^{2}

**i**since it is v

^{2}is not a vector...How do i determine its direction using vector methods?

a) Free-fall starting from rest, downwards as positive.

(Common sense) Opposes motion:

b) Free-fall starting from rest, upwards as positive.

The object is moving downwards, hence velocity is negative. To oppose velocity, resistive force points downwards.

However, I got all my directions wrong when taking the upward as positive! I don't know what is wrong with my reasoning!