What are the x and y components of the velocity of the CM of the two bodies?

[jayced]

Homework Statement

Body A of mass 3 kg is moving int he x+ direction with a speed of 14 m/s. Body B of mass 4 kg is moving in the -y direction with a speed of 7 m/s. What are the x and y-components of the velocity of the CM of the two bodies?

The answer is (6m/s,-4m/s).

Homework Equations

CMx=m1x1x+m2x2/m1+m2

The Attempt at a Solution

I am not getting the answer when I enter the figures into the equation. Is this the right equation? Please help it seems simple once I get the right equation.

 

[PhanthomJay]

It seems from the solution that the 3Kg and 4kg blocks are reversed. Body A appears to be 4 kg, and Body B appears to be 3 kg.

 

[jayced]

I'm still confused so if they are reversed can I ask what equation would I use to calculate x and y components?

 

[ehild]

The coordinates of the CM in case of two bodies:

$$x(CM)=\frac{x_1m_1+x_2m_2}{m_1+m_2}$$

$$y(CM)=\frac{y_1m_1+y_2m_2}{m_1+m_2}$$

The same holds for the components of velocity:

$$V_x(CM)=\frac{v_{x1}m_1+v_{x2}m_2}{m_1+m_2}$$

$$V_y(CM)=\frac{v_{y1}m_1+v_{y2}m_2}{m_1+m_2}$$

ehild