Indiana Jones is swinging from a rope. The distance between the pivot point and his center of mass is 31.00m. He begins swinging from rest at an angle theta=20.00 degrees. Assuming that Indiana and the rope can be treated as a simple pendulum, what is the value of theta after 1.390s (in degrees)?

Answer 1

First calculate the period of a complete swing back and forth. It is
P = 2 pi sqrt(L/g)
which is about ten seconds
In 1.39 seconds, he will not have reached the lowest position (zero degrees) yet.

Theta ( in degrees) = 20 cos (2 pi*t/P)
Use your P and t to calculate theta at that time