Calculating Mass and Gravity on Planet Newtonia

[pdiddy94]

On the planet Newtonia, a simple pendulum having a bob with mass 1.00 and a length of 195.0 takes 1.40 , when released from rest, to swing through an angle of 12.5 , where it again has zero speed. The circumference of Newtonia is measured to be 51400 .

I solved for g using T = 2pi*sqrt(L/g) and then i used this g plus the constant G and the radius solved from the given circumference to calculate the mass of the planet from the equation g = GM/R^2 but can't get the answer, i don't know if its because I'm not taking the angle into account?

 

[tiny-tim]

welcome to pf!

hi pdiddy94! welcome to pf!

… takes 1.40 , when released from rest, to swing through an angle of 12.5 , where it again has zero speed.
…
… i don't know if its because I'm not taking the angle into account?

the angle makes no difference (so long as it's reasonably small, as 12.5° is),

but the period T is for two swings, isn't it?

 

[pdiddy94]

ohh, thank you that makes sense