Physics
posted by charlie .
For a child's swing in lightly damped SHM, I am given the time period and a value for g; (as well as the mass.)
with just these, can i rearrange the equation:
T (4s)= 2pi times sqrt l/g
to calculate the length of the swing?
I believe i have (3.98m), but the question says to ignore the mass of the ropes. I'm worried i should use mass, but it seems uneccessary.
Any help appreciated.

Ignore the mass. Yes, you have the correct formula to solve for length. Remember Galileo sat in church observing the periods of the swinging chandeliers. He concluded the size of the chandelier (mass) made no difference, just the length of the chain holding it.