← Components and relative motion

Sketch the components

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

A soccer ball leaves a boot at 10 m/s, aimed 30° above the horizontal. Part of that velocity carries the ball forward. Part of it lifts the ball upward. One slanted arrow is doing two jobs at once.

10 m/s30°
The ball's velocity on its own: one slanted arrow, two jobs.

In the last lesson you saw that any vector can be replaced by a horizontal component and a vertical component with the same effect. This lesson shows how to draw the two components.

Start with the vector itself: one arrow, 10 m/s long on your scale, aimed 30° above the horizontal.

From the vector's tail, draw a horizontal arrow along the ground direction. End it directly below the vector's tip. This arrow is the horizontal component.

From the tip of the horizontal arrow, draw a vertical arrow up to the vector's tip. This arrow is the vertical component.

horizontal componentvertical component10 m/s30°
The components drawn in: the horizontal leg starts at the vector's tail, and the vertical leg closes the triangle at the tip.

The three arrows now form a right triangle. The two components are its legs, and the legs meet at 90°. The vector itself is the hypotenuse, the longest side.

A sketch resolves an 18 m/s velocity aimed 50° above the horizontal into components. Which arrow is the triangle's hypotenuse?

In a component sketch, the two components meet at what angle?

The sketch must tell the truth about the angle. A vector aimed 30° above the horizontal has a horizontal component longer than its vertical component. A steeper vector, aimed above 45°, has the longer vertical component.

The construction in one line: the horizontal component runs from the vector's tail and ends directly below the tip; the vertical component rises from that point to the tip; the vector itself is the hypotenuse. Label the angle at the tail, the magnitude on the hypotenuse, and each component's name on its leg.

Describe the component sketch of a hang glider's 24 m/s velocity, aimed 55° above the horizontal.

horizontal componentvertical component24 m/s55°

Draw the velocity first:

one arrow, 24 m/s on the scale, at 55° above the horizontal

Draw the horizontal component:

from the arrow's tail, ending directly below the tip

Draw the vertical component:

from that point, up to the tip

Check the proportions: 55° is above 45°, so the vertical leg is drawn longer than the horizontal leg.

A right triangle: the 24 m/s velocity as hypotenuse, a shorter horizontal leg, a longer vertical leg.

Selma sketches the components of a 15 m/s velocity aimed 40° above the horizontal. She says the two components and the velocity arrow form a right triangle, and the velocity arrow is the longest side. Is she correct?

Your turn

A sketch shows a delivery drone's 12 m/s velocity, aimed 65° above the horizontal, as the hypotenuse of a right triangle. One leg lies parallel to the ground. What does the other leg show?

In a correct component sketch of a vector, where does the horizontal component begin?

A velocity is aimed 60° above the horizontal. In a correct component sketch, which statement about the two components is true?