# Homework Help: Pendulum homework problem help

1. Dec 6, 2009

### mattmannmf

original pendulum of mass 11 kg with a period of 1.6 sec, displaced an angle of 12 degrees from the vertical. What would its acceleration be in the vertical (y) direction as it reachs the lowest point on its swing?

wouldn't it just be -9.8? (since its just the force of gravity acting on it)

2. Dec 6, 2009

### denverdoc

Re: Pendulum

It is a pendulum, which means it is attached by a rod or string. In either event, what does that do to the force of gravity at the low point?

3. Dec 6, 2009

### mattmannmf

Re: Pendulum

umm...not sure...

4. Dec 6, 2009

### denverdoc

Re: Pendulum

Well if you look at the free body diagram the tension in the rod cancels out the force of gravity.

5. Dec 6, 2009

### mattmannmf

Re: Pendulum

ok so its just zero

6. Dec 6, 2009

Re: Pendulum

yep.

7. Dec 6, 2009

### AakashR

Re: Pendulum

you need more information to solve the problem. you need to know the tension in the rod or string that's supporting the pendulum. Then you will be able to solve the eqn
ΣF=ma=mg-T Cos θ