Simple (supposedly) pendulum with unknown length and kinetic energy

[VinnyCee]

Please help, if a 60 g bob at the end of a cord (unknown length) of negligable mass and the angle $$\Theta = (0.0800 radian) cos[(4.43 radian / s.) t + \phi]$$ <---- Angle between cord and the vertical.

What are
a) the pendulum's length?

b) it's maximum kinetic energy?

Please help, the prof did not go over any of this type of problem.

 

[Tide]

The 4.3 rad/s is the angular frequency which is related to the length of the pendulum. Can you take it from there?

 

[Justin Lazear]

Google is a wonderful thing.

http://hyperphysics.phy-astr.gsu.edu/hbase/pend.html

If you don't understand about pendulums, I'd suggest learning about the system before throwing numbers at equations.

--J

 

[VinnyCee]

Ok, I gto part a) but not part b). Please help

a) 0.494 meters

But how do I relate that to find the x_max?

 

[HallsofIvy]

The kinetic energy will be highest when speed is highest. At what point is the speed of the pendulum highest? (If by x_max, you mean the highest point the pendulum reaches, that is irrelevant.)