Homework Help: Calculating Tension For A Massless String

1. Feb 8, 2013

Yosty22

1. The problem statement, all variables and given/known data
A gymnast of mass 59.0kg hangs from a vertical rope attached to the ceiling. You can ignore the weight of the rope and assume that the rope does not stretch. Use 9.81 m/s^2 for the value for the acceleration of gravity.
Calculate the Tension, T, in the rope if the gymnast climbs the rope at a constant rate.

2. Relevant equations

None (that I can think of)

3. The attempt at a solution

Since the rope is massless, I was thinking that the tension on the rope if she hangs there motionless should be the same as if she is climbing it. Solving for the Tension of the rope while she was sitting there, I just used mass times gravity, in this case; 59kg*9.81m/s^2=578.79N. Would this answer be the same if she was climbing up the rope as well?

2. Feb 8, 2013

Staff: Mentor

Right, but that is true for a massive rope as well.
Yes. You can use momentum conservation to show this, for example.

3. Feb 8, 2013

Yosty22

This is true as long there is no acceleration, correct? As long as the velocity is constant, that is always true?

4. Feb 8, 2013

Staff: Mentor

Yes - if we assume that the gravitational force does not depend on the height (a very good approximation here...).