I've tried to just difference the times but I feel like im missing another equation to use or im doing smth wrong. Any help would be greatly appreciated.
You seem to be a fair bit off. As in the hints the time period for a pendulum is 2pisqrt(l/g) and you want to think about how the period(s) relate to breaking the laser beam for the two pendulums. The actual perturbation is a bit of a red herring.
Also the hints suggest thinking about the shorter pendulum first, then the longer one and thats a good hint.
Though now im not sure what the time difference represents - is this value equal to 0.3s - how is the difference between the times determined?
The half period for the shorter pendulum is 0.3s (which I think youre saying) so the length is ...
Id use a more descriptive label(s) for time, so 1/4 period until it first cuts, then 3/4 period until it cuts again or by symmetry, 0.3 s must be a 1/2 period.
Then think about the second pendulum and how to minimise the (total) length.
Ok I think I get what the question is asking? So the time taken for the first pendulum to complete a half period is 0.3s so I can work out l1. In this time the second pendulum completes a quarter period barely reaching the laser (which I think would give the lowest length) so I can work out l2.
Ok I think I get what the question is asking? So the time taken for the first pendulum to complete a half period is 0.3s so I can work out l1. In this time the second pendulum completes a quarter period barely reaching the laser (which I think would give the lowest length) so I can work out l2.
Sounds close but not quite right for the longer pendulum