Man and boy collide on ice, find boy's initial velocity

[dbb2112]

Homework Statement

A 70kg man who is ice skating north collides with a 30kg boy who is ice skating west. Immediately after the collision, the man and boy are observed to be moving together with a velocity of 2m/s in a direction 37 degrees north of west. What was the magnitude of the boy's velocity before collision.

Homework Equations

The Attempt at a Solution

I do not really know where to start. Could someone please list equations that are needed for this problem.

 

[dbb2112]

i meant to title inelastic

 

[LogicalTime]

use conservation of momentum, you should have an equation for the y-axis (north/south) and an equation for the x-axis (east/west)

 

[dbb2112]

I do not see how to use it when only the final velocity is given.

 

[dbb2112]

ok I am not sure if this is right, but i made the equation m2v2cos=m1v1'cos+m2v2'cos
and found v2 to equal 2.13 would that be my final answer?

 

[LogicalTime]

usually good to break these down into momentum in x direction and y direction

$M_{man}V_{man} \hat{y} = M_{final}V_{yfinal} \hat{y}$
$M_{boy}V_{boy} \hat{x}=M_{final}V_{xfinal} \hat{x}$
$M_{final} = M_{boy} + M_{man}$
$V_{yfinal} = \left( 2 \frac{m}{s} \right) cos(37^{\circ})$
see if you can determine the other final V and solve, let me know if you have questions on notation and such

 

[dbb2112]

Thanks I am good now

 

[LogicalTime]

xcellent,

"may entropy increase in a way that favors your sword"
-Logicaltime