Posted by Jennifer on .
A 650 N boy and a 490 N girl sit on a 150 N porch swing that is 1.70 m long. If the swing is supported by a chain at each end, what is the tension in each chain when the boy sits .75 m from one end and the girl .5 m from the other end?

Physics HELP! 
drwls,
The sum of the two chain tesnions is
T1 + T2 = 650 + 490 = 1140 N
Take moments about the chain nearest to the girl and set the sum equal to zero. Call the cable nearest the boy "1". The boy is 0.95 m from the girl's end, "2".
T1*1.7 0.95*650  0.5*490 = 0
Solve for T1. Then use T1 + T2 = 1140 N to solve for T2. 
Physics HELP! 
Jennifer,
Shouldn't we consider the weight of the swing as well?

Physics HELP! 
drwls,
Yes. Good thinking. I overlooked it

Physics HELP! 
Jennifer,
So then assuming the swing is uniform, do I have:
T1 + T2 = 650 + 490 + 150 = 1290 N
Then,
T1*1.7 0.95*650  0.5*490 .85*150 = 0
Solve for T1 and then use the first equation to solve for T2? 
Physics HELP! 
drwls,
Yes. :)

Physics HELP! 
Abby,
how is this equation right? when i multiplied all those numbers to get T1 i got a huge number...to plug it back in for T2 i would get a negative number...