Conservation of Momentum and Energy in Fisherman-Boat Interaction

[Ronaldo21]

Basic Momentum and Energy!

Note: Take East as the positive direction. A(n) 88 kg fisherman jumps from a dock
into a 123 kg rowboat at rest on theWest side of the dock.
If the velocity of the fisherman is 4.1 m/s to the West as he leaves the dock, what is the
final velocity of the fisherman and the boat?
Answer in units of m/s.

so do i just do 88 times 4.1 and get 36.08
then do (88+123)v and get 211v
then do 36.08=211v and solve for v??

 

[ideasrule]

Yes, because initial momentum = 88*4.1 and final momentum=(88+123)v.

 

[Ronaldo21]

no because i did that and got 360.8 = 211V
then i solved for v and got 1.709952607 and it said i got it wrong.
did i do anything wrong?

 

[Nowayz]

Look at what direction is positive. You solved correctly

The answer would be -1.71m/s

 

[Ronaldo21]

-? why negative??

 

[ideasrule]

Right, trick question! "Note: Take East as the positive direction."

 

[Ronaldo21]

ohh! gotcha!
thank you very much!