Physics

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For this problem there is a picture of pendulums. They are numbered 1 through 5. Each pendulum is a certain length and has a washer at the end.

1) the weight is 5w.
2) this is the longest one and the weight is 3w.
3) weight is 5w.
4) weight is 10w
5) this is the shortest one and the weight is 4w.

There are a few questions for this that I really do not understand.

1) Suppose you wanted to do an experiment to find out if changing the length of the pendulum changed the amount of time it takes the pendulum to swing back and forth. Which pendulums would you use?

1 and 4, 2 and 4, 1 and 3, 2 and 5

I think the answer is 2 and 5 because you should test the longest to the shortest. Is this correct?

2) Suppose you wanted to do an experiment to find out if changing the weight on the end of the string changed the amount of time the pendulum takes to swing back and forth. Which pendulums would you use?

1 and 4, 2 and 4, 1 and 3, 2 and 5.

I think the answer is 2 and 4 because the heaviest weight should be compared to the lightest weight. Is this correct?

• Physics -

right on 1)
But the second, if you chose 2 and 4, you also not only have a weight change, but a length change. I would do 1 and 4, varying only weight.