# Unknown variables.

1. Dec 6, 2009

### dois

1. The problem statement, all variables and given/known data

Two chain links are connected together and are suspended by a string. The mass of the top link, link#1 is 8kg, while the mass of the second/bottom link #2 is unknown. If an applied force on the string attached to link #1 of 216N[up], and the links experience an acceleration of 2m/s^2 [up] find the mass of link #2 and the force that link#2 exerts on link1

2. Relevant equations

The only thing I know is that the mass is equal to the mass of both of the chains put together, so the mass is greater than 8kg.

3. The attempt at a solution
I'm not sure what equations I would have to use

2. Dec 6, 2009

### denverdoc

F=ma=sum of all forces. Force 1 is upwards=216. Force downwards is due to gravity.

To start, consider a tota mass which is equal to m1 + m2 =M m1=8, m2=?

2*M=(216-Mg) Can you get m2?

3. Dec 6, 2009

### dois

if we were to sub all of our knows into the equation 2 x M= (216-mg) we would get

2 x M= (216 - m x 10)

but then where would we go from there

4. Dec 6, 2009

### denverdoc

Well this (M) is the total mass. So subtract m1 and you have the unknown mass. Then if you do a Free body diagram, the force that link 2 exerts on link 1 is easily obtained--it is just the weight of link 2 (note weight is not same as mass)