# Two-dimensional motion

1. Jul 12, 2007

### MIA6

Motion in one dimension means that something always runs in a straight line? So how about two-dimensional motion? What does that mean literally?For instance, Why projectile is a two-dimensional motion? It's a parabolic path? so what does 'two-dimensional' mean here? thanks.

2. Jul 12, 2007

### bel

It means that there is a level plane, for which if the path were projected onto it, the path would remain unchanged.

Last edited: Jul 12, 2007
3. Jul 12, 2007

### MIA6

ok, here is a question: A hummingbird, 3.4m above the ground, flies 1.2m along a straight path. Upon spotting a flower below, the hummingbird drops directly downward 1.4m to hover in front of the flower. What is the hummingbird's total displacement? I can't imagine a pic in my head.
Humming bird-------- (1.2m) flies
/
/
/
/ (3.4m)
-------- (ground) but where is the flower?

4. Jul 12, 2007

### Chi Meson

2 dimensional motion refers to motion that can be depicted on a simple graph with x and y coordinates. A parabola, as you follow it's path, changes both its x position and its y position. A projectile follows a parabolic path, and as it moves, it changes its horizontal (x) and vertical (y) positions simultaneously.

If you threw a curve ball, then it would also move sideways, as it moved forward and down, but that's getting too complicated too quickly.

In the hummingbird question, this is not a projectile problem. The hummingbird moves a horizontal distance, then a vertical distance. Draw a straight line horizontally, then at the end of that line, draw one downward. This is the path of the bird.

Now find the displacement, which is the straight line between the starting point and the ending point. Do you see a triangle?

5. Jul 12, 2007

### MIA6

yes, OHH, i thought the flies is a noun, not a verb which means 'fly'. ok, thank you.