Indiana Jones rope swing physics

[zhenyazh]

Hi,
I am preparing for a test and have the following question.
there is the image attached too.

Indiana Jones is swinging from a rope. The distance between the pivot point and his center of mass is 31.0 m. He begins swinging from rest at an angle θ = 19.0o as shown in the figure. Assuming that Indiana and the rope can be treated as a simple pendulum, what is the value of θ after 1.27 s (in degrees)?

so i this is a harmonic motion question. as far as i understand i can use the
formula of location (x=...) but use angles to represent the location and thus get the answer. but somehow i get the wrong answer all the time.
could some one show me how it is done so i can see where i am wrong?

thanks

 

[tiny-tim]

Hi zhenyazh!

… so i this is a harmonic motion question. as far as i understand i can use the
formula of location (x=...) but use angles to represent the location and thus get the answer. but somehow i get the wrong answer all the time.
could some one show me how it is done so i can see where i am wrong?

thanks

Show us your full calculations, and then we'll see what went wrong, and we'll know how to help!

 

[zhenyazh]

ok.
so indiana starts from the farthest point and i want to work in degrees and not meters t to find position.
so i say x=Acos(wt+fi)
where A=19 deg, t=.127 and w=sqrt(g/l) where l is 31 if i understand the question correctly.
the answer i get is wrong.

 

[tiny-tim]

Hi zhenyazh!

(have an omega: ω and a phi: φ and a square-root: √ )

ok.
so indiana starts from the farthest point and i want to work in degrees and not meters t to find position.
so i say x=Acos(wt+fi)
where A=19 deg, t=.127 and w=sqrt(g/l) where l is 31 if i understand the question correctly.
the answer i get is wrong.

Isn't t = 1.27 ? And what did you use for φ ?

 

[zhenyazh]

about the time yes you are right, it is a type.
about fi, i used zero since i use cos for my calculation and start from the right amplitude