# Relative Motion

#### PhysicsGenius

1. The problem statement, all variables and given/known data
I am given the location of 3 points in space:
Z1= X_1+Y_1i
Z2= X_2+Y_2i
Z3= X_3+Y_3i

and the velocity of two points:
V_1= X_1+Y_1i
V_2= X_2+Y_2i

How do I find V3?

2. Relevant equations
V_1/2= V_1-V_2
V_3= V1+V_3/1
V_2/1= V_2-V_1

3. The attempt at a solution

I have the equations, but I just can't seem to figure out how to relate V_3 with V_2 and V_1. Can anyone help?

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#### PhysicsGenius

Please help, I know it's something simple that I'm missing.

#### Liquidxlax

your name is a lie... lol

but seriously, if you could type it out a little more clearly i can help

#### PhysicsGenius

your name is a lie... lol

but seriously, if you could type it out a little more clearly i can help
lol I know, I just wish I was a genius What do you mean by more clearly? Let me put some numbers into the equations
I am given the location of 3 points in space:
Z1= 3+3i
Z2= 7+5i
Z3= 5+5i

V_1= 8+0i
V_2= 7+6i

How do I find V3?

2. Relevant equations
V_1/2= V_1-V_2
V_3= V1+V_3/1
V_2/1= V_2-V_1

Any help? Thanks.

#### Liquidxlax

i don't see how you can find velocity, with just position vectors and velocity. You have no time or initial position. Are you sure your putting everything in?

What textbook is this from?

#### PhysicsGenius

i don't see how you can find velocity, with just position vectors and velocity. You have no time or initial position. Are you sure your putting everything in?

What textbook is this from?
Yes that is the entire problem, you are supposed to solve by using relative velocity. The equations I listed are a start, but I'm not sure where I go from there.

#### The legend

really, i don't think there's a way to solve this without something else given ..
ideas anyone?

#### PhysicsGenius

The problem also states that the 3 points are on the same link, if that helps.

Any ideas?

no 1

#### zgozvrm

1. The problem statement, all variables and given/known data
I am given the location of 3 points in space:
Z1= X_1+Y_1i
Z2= X_2+Y_2i
Z3= X_3+Y_3i

and the velocity of two points:
V_1= X_1+Y_1i
V_2= X_2+Y_2i

How do I find V3?

2. Relevant equations
V_1/2= V_1-V_2
V_3= V1+V_3/1
V_2/1= V_2-V_1

3. The attempt at a solution

I have the equations, but I just can't seem to figure out how to relate V_3 with V_2 and V_1. Can anyone help?
This is like saying:
There are 3 cars. Car A is traveling due East at 50 mph. Car B is traveling due north at 75 mph. What is the velocity of car C?

You don't have enough information to answer the question!!!!!

#### nvn

Science Advisor
Homework Helper
Last edited by a moderator:

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