a) Why? A swinging chain keeps time.
Quotewith a known string length LA pendulum should be rigid.
with a known string length L
Why is the photogate method I described a far easier method of measuring gravity than an accelerometer?Well there was quite a bit of discussion about using cheap off the shelf accelerometers and I never did see anyone having a solution that actually did measure the acceleration due to gravity, without first assuming what it was to begin with. By using the photogates you can easily derive the solution for the acceleration due to gravity based on first principles, and not by assuming what the result is you are looking for. The photogate method is used in first-year physics labs everyday, I used to have my first year students derive the solution for homework, tests, or labs.