- #1
bcjochim07
- 374
- 0
Homework Statement
What is the amplitude of a pendulum whose angle is given by (.10 rad)cos(5t + pi)
where t is in sec.
Homework Equations
s(t)=Acos(omega*t+phase constant)
Theta(t)=thetamax*cos(omega*t+phase constant)
The Attempt at a Solution
I'm not quite sure if I did this right:
I found the length of the string to be .392 m ( by using omega= sqrt(g/L)
So, using the small angle approximation s= .392 * sin theta where theta= the intial angle, which I found to be .1 rad by looking at the equation
s=(.392*sin(.1rad)) = .039 m
Then I used s(t) =Acos(omega*t + phase constant) with t=0
I also found omega= 5 and the phase constant is pi
.039 m = A cos(pi)
But my amplitude ends up negative. I've having a bit of trouble with positive and negative signs in SHM