1. ## 2D Physics Inquiry.

Hi, my question corresponding to 2 dimensional physics problems is that: why when given an initial speed of let's say a ball being thrown in the air ( Vi= 23 m/s at 23 degrees relative to the human), why is the velocity of the y component Vy= 23m/s (sin 23) ? My teacher did this in class today and I am a bit confused. Would that mean the velocity of the x component is: Vx=23m/s(cos 23) ?

By the way, I am not confused by the sine or cosine because I know sine relates to the y axis and cos to the x axis.

2. ## Re: 2D Physics Inquiry.

Originally Posted by sakonpure6
Hi, my question corresponding to 2 dimensional physics problems is that: why when given an initial speed of let's say a ball being thrown in the air ( Vi= 23 m/s at 23 degrees relative to the human), why is the velocity of the y component Vy= 23m/s (sin 23) ? My teacher did this in class today and I am a bit confused. Would that mean the velocity of the x component is: Vx=23m/s(cos 23) ?

By the way, I am not confused by the sine or cosine because I know sine relates to the y axis and cos to the x axis.

yes, the x velocity component will be 23 cos(23degrees) m/s (you should get used to including units)

3. ## Re: 2D Physics Inquiry.

would that work with other units like displacement or acceleration?

4. ## Re: 2D Physics Inquiry.

any and all 2D vectors

it gets a bit more complicated in higher dimensions but the basic idea is the same. The length of the component of a vector along some axis is the vector dotted with the unit vector along that axis.

In 2D the usual unit vectors are (1,0) and (0,1) and you can work out that the dot product of a vector corresponds to the diagram i drew you.