# Newton's law trick? question

1. Jun 9, 2009

### iamtrojan3

Newton's law "trick?" question

1. The problem statement, all variables and given/known data
A 40 kg girl and a 50 kg boy are on the surface of a frozen lake, 10 m apart. Using a rope, the girl exerts a horizontal 5.0 N force on the boy, pulling him toward her. Calculate the magnitude of the girl's acceleration.

2. Relevant equations

F=ma

3. The attempt at a solution
i don't really know where the distance from the problem comes in and its not as simple as it looks... apparently.
I thought about how if the girl pulled the rope with 5N then the only mass that's moving is the boy, but that wasn't right. Adding the weights together didn't work either.
THe hint i got was "newton's 3rd law"
how will that apply to this problem? i understand the concept of the 3rd law.

Thanks!

Last edited: Jun 9, 2009
2. Jun 9, 2009

### bp_psy

Re: Newton's law "trick?" question

Then what would be the force on the girl?

3. Jun 9, 2009

### iamtrojan3

Re: Newton's law "trick?" question