← Vectors: drawing, measuring and combining

Any vector splits into two perpendicular components

So far, two vectors have become one: a 6 m/s east velocity and an 8 m/s north velocity act exactly like one 10 m/s velocity aimed 53° north of east.

The trade also runs backwards: one vector can be swapped for two.

Run the replacement in reverse: the single 10 m/s velocity can be replaced by 6 m/s east plus 8 m/s north. The pair has the same effect. Any vector can be replaced like this: a horizontal piece plus a vertical piece that together have the same effect as the original.

The two replacement vectors are called the original vector's components. The horizontal one is its horizontal component; the vertical one is its vertical component.

Here is one vector: 10 m/s, aimed 37° above the horizontal.

10 m/s37°
One vector: 10 m/s, aimed 37° above the horizontal.

That velocity acts exactly like 8 m/s horizontal plus 6 m/s vertical.

horizontal component: 8 m/svertical component: 6 m/sthe original: 10 m/s at 37°
The same vector replaced by its two components: 8 m/s horizontal plus 6 m/s vertical, the same effect.

A 20 m/s velocity is replaced by its two components. Which statement must be true?

Horizontal and vertical are perpendicular, so a vector's two components always meet at a right angle.

Alba says: 'A thrown ball's velocity, aimed above the horizontal, can be replaced by a horizontal velocity plus a vertical velocity with the same effect.' Is Alba correct?

Neither component is half of the original. The two sizes are usually different: the vector's direction fixes them.

horizontal: 3.4 m/svertical: 9.4 m/sthe original: 10 m/s at 70°70°
The same 10 m/s aimed steeper, at 70°: the direction fixes the sizes. Now 3.4 m/s horizontal plus 9.4 m/s vertical.

Kofi says: 'A 12 m/s velocity's components must each be 6 m/s.' Is Kofi correct?

Together is the test: the two components, acting together, must do exactly what the original vector does.

A soccer ball leaves a kick at 26 m/s, aimed above the horizontal. What pair of vectors can replace that velocity with the same effect?

Write down the fact:

any vector can be replaced by a horizontal piece plus a vertical piece with the same effect

Its horizontal component plus its vertical component.

A 15 m/s velocity aimed 20° above the horizontal is replaced by its two components. Acting together, what must the pair do?

Write down the fact:

components are defined by one test: the same effect as the original

Exactly what the original 15 m/s velocity does: the same effect.

Type the name for the two perpendicular vectors that together replace a single vector with the same effect.

Your turn

A 34 m/s velocity aimed above the horizontal is replaced by its components. Which statement is correct?

Mira replaces a 9 m/s velocity aimed above the horizontal with its two components. Which statement about the components' sizes is correct?

A 25 m/s velocity is aimed 40° above the horizontal. Which pair of vectors could replace it with the same effect?