# Momentum Surfboard Walking

## Homework Statement

A 32 kg boy is standing on a 59 kg raft that is 8 m wide. He walks 6 m from a point 1.0 m from the left edge of the raft to a point 1.0 m from the right edge of the raft. If you ignore resistance of the water to the motion of the raft, how far does the raft move during this procedure

F=ma
p=mv

No idea

## The Attempt at a Solution

i draw a force diagram for it and looks like the one that will effect the movement of the boat is

F = friction force
but I have no idea what the friction constant is. and also will the mass affect the movement of the boat?

and I also dont have any velocity to use the equation of

m1v1 + m2v2 = m3v3
32(v1) + 0 = 91(v3)

PeterO
Homework Helper

## Homework Statement

A 32 kg boy is standing on a 59 kg raft that is 8 m wide. He walks 6 m from a point 1.0 m from the left edge of the raft to a point 1.0 m from the right edge of the raft. If you ignore resistance of the water to the motion of the raft, how far does the raft move during this procedure

F=ma
p=mv

No idea

## The Attempt at a Solution

i draw a force diagram for it and looks like the one that will effect the movement of the boat is

F = friction force
but I have no idea what the friction constant is. and also will the mass affect the movement of the boat?

and I also dont have any velocity to use the equation of

m1v1 + m2v2 = m3v3
32(v1) + 0 = 91(v3)

This is just a centre of mass question. The centre of mass of the system will remain stationary. The c of m of the two components moves. Where will they each finally be?

This is just a centre of mass question. The centre of mass of the system will remain stationary. The c of m of the two components moves. Where will they each finally be?

x1 = (m1x1 + m2x2) / (m1+m2)
91(1) + 91(7) / (182)
x1 = 4m

uhmm i believe i did something wrong PeterO
Homework Helper
x1 = (m1x1 + m2x2) / (m1+m2)
91(1) + 91(7) / (182)
x1 = 4m

uhmm i believe i did something wrong suddenly the boy and raft have become 91 kg each???

suddenly the boy and raft have become 91 kg each???

x1 = (m1x1 + m2x2) / (m1+m2)
x1 = (32(1) + 59(4)) / (91)
x1 = 2.725

x1 = (m1x1 + m2x2) / (m1+m2)
x1 = (32(7) + 59(4)) / (91)
x1 = 5.055

x = 5.055 - 2.725
x = 2.33m

but it's wrong, I'm confused where my error is

Last edited:
nvm, it was just a miscalculation, i got it now, thank you :)