Simple Pendulum Problem this one's kinda tough

[cheechnchong]

A simple Pendulum is made from a 0.65-m-long string and a small ball attached to its free end. The ball is pulled to one side through a small angle and then released from rest. After the ball is released, how much time elapses before it attains its greatest speed?

My Approach:

I used this equation: 2(3.14 or pi)(frequency) = sq(g/L)

2(3.14)f = sq(9.81 m/s^2/0.65m)

f= 0.618 s-1

THEN,

i found the Period, T.

T = 1/0.618 = 1.62 s

^^answer is not quite there...doesn't correspond with book answer

 

[radou]

Think it through again. What exactly does the period 2 Pi Sqrt(L/g) represent? When does the ball attain its greatest speed?

 

[cheechnchong]

Think it through again. What exactly does the period 2 Pi Sqrt(L/g) represent? When does the ball attain its greatest speed?

^^^V = Amplitude x Angular Speed ? how do i get the Amplitude if that is the case?

 

[cheechnchong]

^^^bump...

 

[AndrewNette]

I had the same problem on an assignment. You are right to calculate the period but you have to figure out when V max is first reached. If the period is the time it takes to move through one whole cycle then the time it takes to reach position zero at first must be one quarter of that time