# Homework Help: Pendulum Difficulties.

1. Jun 7, 2007

### Soley101

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

I have a lot of questions, but once I understand this I will get the basis for the other problems:
Calculate the maximum speed of the 100g pendulum mass when it has a length of 100 cm and an amplitude of 50cm.

2. Relevant equations
?

3. The attempt at a solution

? nothing seems of usefulness, i dont know the questions i should ask myself

2. Jun 7, 2007

### dontdisturbmycircles

Draw the pendulum at its highest point (amplitude of 50cm). What forces act on the ball at this point?

Use the conservation of energy and a bit of trig.

3. Jun 7, 2007

### Soley101

is there any way i can use the pythagorean theorem to solve this?

Last edited: Jun 7, 2007
4. Jun 7, 2007

### Soley101

can the pythagorean theorem be used for this?

5. Jun 7, 2007

:surprised

6. Jun 7, 2007

### rootX

potential energy @ the top == kinetic energy @ the bottom

You dun need Pythagorean theorem.

7. Jun 7, 2007

### Soley101

i know i dont need it, but can it be done?

8. Jun 7, 2007

### rootX

no, it cannot be used.

do you know about these formulas:
U = mgh
K = 0.5mv^2
?

You need to use those two.

9. Jun 7, 2007

### Soley101

no i dont know tose. argh im frustered

10. Jun 7, 2007

### Soley101

what is u and what is k

11. Jun 7, 2007

### Soley101

I think my main problem is not knowing what the height is!!!!!! b/c it doesn't seem like an amplitude on a pendulum can be the height, it seems more like the distance away from center.?

12. Jun 7, 2007

### Soley101

13. Jun 7, 2007

### rootX

You should know those formulas before touching this question.
So, it might be good if you read a little about conservation of energy.
For sure, that would help.

I am assuming that you have a book, if you dunn, just reply and I will provide a link for that.

14. Jun 7, 2007

### lalbatros

"can the pythagorean theorem be used for this?"

somehow yes

you know the hypthenuse (length)
you know the angle or angular amplitude of the motion (from the ampltude)