# Pendulum Momentum Problem

#### Eternal Ophidian

I have to solve this problem but every answer I've come up with so far has been wrong. If any one knows how to solve it, I'd greatly appreciate some enlightenment. Thanks.
Here's the question:
Two pendulums are hung adjacent to each other as shown in Fig. 7.20. Bob 1 has a mass m, and bob 2 has a mass 3m. Bob 1 is pulled aside until the support string makes an angle of 45° with the vertical direction and then is released. When the bobs collide, they stick together. What is the maximum angle made by the support strings with respect to the vertical after the collision?

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#### joc

arccos [ [30 + sqrt(2)] / 32 ]
= arccos [ 0.9817 ]
= 79.0 degrees?

#### StephenPrivitera

In order to find the maximum angle that the two balls rise to, you need to know the velcoity of the two balls after the collision. This is easy to find using conservation of momentum
m1v1+m2v2=(m1+m2)v'
One of the balls is initially at rest, so the problem is even easier.
m1v1=(m1+m2)v'

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