Finding maximum speed using work energy theorem without integration

[Clara Chung]

Homework Statement

Homework Equations

The Attempt at a Solution

I don't know how to do part 5, I know the point of maximum speed is at an angle of 120 degrees because the work starts to be negative, but how do I find of the maximum speed at that point without using vector integration? (I tried to integrate from theta = 0 to 2 pi /3 but I think it is a bit complicated for a 4 marks question.)

 

[haruspex]

how do I find of the maximum speed at that point without using vector integration

Nevertheless, if you write the integral and bear in mind that $\vec F$ is constant you may find it is quite easy.