I dont not understand velocity and speed in two dimensions. My teacher barely explained it and i do not know what to do except for the part of finding out the coordinates. Anyways heres a question i hope you will be able to help me with.

 

Determine the vector sum of the displacements d1= 2.4 m [32 degrees S of W]; d2=1.6 m ; and d3= 4.9 m [27 degrees S of E].

do i add one and subract the rest i dont get it.

 

This is what i did so far, is this right?

 

drx= d1+d1+d3

=2.4cos32 - 1.6 - 4.9cos63

=2.08 - 1.6 - 2.22

= -1.79

 

dry= d1 + d2 + d3

=2.4sin32 - 1.6 - 4.9sin63

=1.27 - 1.6 - 4.365

= -4.695

 

I dont know whether i was supposed to add these or subtract them. If this is right what do i do from here??

you're supposed to add them.

 

it may be easier(especially once you get more into kinematics) to put the vectors in the form [math]\vec{v}=<a_1,a_2>[/math]. it makes things like addition and products much easier.

But they are going in different directions, so how am i supposed to add them. Does that mean i did it wrong. Also after i get x resultant and my y resultant what am i supposed to do now?

it doesn't matter which direction they are in

I get the wrong answer if i add them.

Break them up into orthogonal components (x,y) and add the components.

i did do that up there but i subtracted and i did it again and i added them but i still get the wrong answer so can you like go step by step please

you can't really subtract vectors. you can, however, add the opposite of a vector(A+-B). do it like i said. put it in the v=(x,y) form and add that way. i suppose they want you to find the magnatude in the direction of the vector, so once you've added them, go ahead and use the pythagorean theorem