# SHM - Planet Problem

## Homework Statement

You are exploring a newly discovered planet. The radius of the planet is 7.20 * 107 m. You suspend a lead weight from the lower end of a light string that is 4.00 m long and has mass 0.0280 kg. You measure that it takes 0.0685 s for a transverse pulse to travel from the lower end to the upper end of the string. On the earth, for the same string and lead weight, it takes 0.0390 s for a transverse pulse to travel the length of the string. The weight of the string is small enough that you ignore its effect on the tension in the string. Assuming that the mass of the planet is distributed with spherical symmetry, what is its mass?

## The Attempt at a Solution

I don't really know where to go with this? I was thinking something about comparing the radi of the planets, but I'm not sure??

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Delta2
Homework Helper
Gold Member
What result/formula do you know for the speed of a transverse wave on a string? The speed of the wave is different in the new planet than at earth, because in the new planet the weight of the lead and hence the tension of the string (those two forces will be approximately equal during the experiment) is different.

gneill
Mentor
I don't really know where to go with this?
When you don't know where to start with a problem, try listing all the physics principles that you can recognize being involved in the problem statement. Then list any formulas involved with that physics. That should give you some clues as to how to move forward.