What is the solution to the tricky pendulum question on page 6?

[Chewy0087]

Homework Statement

hey sorry about this again but I'm having trouble with some questions :

http://www.physics.ox.ac.uk/Admissions/undergraduate/admissions_test/tests07.pdf

The Attempt at a Solution

page 6) okay well the bit I'm not sure about here is that L(cm) seeing as it is the distance to the COM i substituted r/2 for the uniform rod and r for the one with the bob giving me;

i guess it makes sense because it would go to my simplified versions when simplified

then with the 24 hour one it's really tricky...

i worked out how much a time period would be to give a difference of 1 day + 1 second, then I worked out what the difference in r would be which gave me;

0.469K for brass and
7.429K for invar, do you think that's reasonable?

note i used the formula for a pendulum of negligible mass and a mass on the end.and

page 10) question 6, I literally have no idea, i KNOW that it's a silly rule or something reguarding a equilateral triangle in a circle or some rule you can draw on however I'm just blank on this one, any pointers in the right direction would be great...

thanks again!

 

[Chewy0087]

bump, i know it's a lot to ask but some help would be great