Solve Pendulum Swing Angle Problem - Physics Adorers

[phunphysics2]

Greetings Physics adorers!

I was wondering if somebody could please check my work for the problem below.

A pendulum with a length 2m has a velocity of 3 m/s at its lowest point. What is the largest angle it creates relative to the horizontal as it swings. Hint: use energy conservation.


Here is my work
mgh=mv^2/2,,,,,,,,,,h=0.459 m,,,,,,,,,cos(angle) = h/r=0.459/2,,,,,,,,,,,angle=76.7 degree


Please let me know if it is correct. If it is wrong, please give suggestions on how I should correct.

Thanks!

 

[grzz]

The value of h is ok.

But note that cos(angle) = (r - h)/r

 

[phunphysics2]

Thank you for your response!

But I am not sure that I understand what you mean

 

[grzz]

Refer to the diagram attached.

 

[phunphysics2]

Thank you for the diagram! so cos (angle)= (2-.459)/(2)

= about 39.60 degrees?