Simple Harmonic Motion , finding the time taken to travel an angular dispalcemnt

[kingkong69]

1. Homework Statement

Find the time taken to reach half the maximum angular displacement in a PENDULUM. Given that the bob hanging at rest was given an initial velocity of 2ms, and the length of the string is 6m.



2. Homework Equations
finding the angular velocity using sqrt.(g/l). where g is 9.8 and l is 6m.
maximum angular displacement with conservation of energy formulas.



3. The Attempt at a Solution

i found the maximum angular displacement and it is 68.8degrees using kinetic=potential energy. The question is half the maximum displacement so i took 34.4 degrees in radians, then i divided it by the angular velocity resulting in a wrong answer

The answer behind the book says 4.1s


Thanks any help is appreciated.

 

[Disconnected]

The velocity is not constant.
What else could you do with the angle you found?

 

[Doc Al]

The speed is not uniform. To solve for the time, write the angular displacement as a function of time. (Hint: There'll be a trig function involved.)

 

[kingkong69]

got it, thanks a lot guys