# I want to try an experiment related to mechanics -- suggestions please

VVS2000
If anyone has an idea for an experiment or has any kind of manual containing experiments related to mechanics, that would really be helpful.
If you have an idea like a new way to find moment of inertia of given object or anything like that, please do tell. I would really love to try it.
Thanks

Mentor
You will get better and more helpful answers if you tell us why you’re asking. Are you looking for something you can do as a school project or something else?

VVS2000
You will get better and more helpful answers if you tell us why you’re asking. Are you looking for something you can do as a school project or something else?
Well I am not able to appreciate or convince myself why we do what we do when I am doing experiments in my lab classes. I thought doing more and more experiments will help me to make some sense of practical physics

Staff Emeritus
Rolling a ball down a slope is a good experiment. But you probably did that already.

So tell us which experiments you did already, so we don't waste our time suggesting things you already did.

sysprog
VVS2000
Rolling a ball down a slope is a good experiment. But you probably did that already.

So tell us which experiments you did already, so we don't waste our time suggesting things you already did.
Good point..
Ok here's what I have done.
Simple pendulum where I tried to find out the damping and also found out large deviations in small angle approximation, along with time period of course.
Similarly for coupled oscillator and spring constant, I actually wanted to try driven harmonic oscillator using magnets as the external force source and hence find the affect of magnets and therefore find the nature of magnetic force, it would be really helpful if anyone can tell me how😅
Ok this is what I have done so far.
If you have anything related to moment inertia or anything interesting in mechanics it would be really helpful!

Fred Wright
Build an Atwood machine, determine the moment of inertia of the pulley by timing the change in position of the known masses of the system and compare with theory.

Gold Member
Build a clock based on gyroscopic precession through the rotation of the Earth.

Fred Wright
Fred Wright
Build a clock based on gyroscopic precession through the rotation of the Earth.
That's a good one!
Edit: However, building a Foucault pendulum is not a trivial undertaking and requires a large volume of lab space.

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Fred Wright
My bad. When I was a 10y.o. my dad (a physicist) brought me to the San Diego museum of natural history to see a Foucault pendulum. The pivot was about 30 feet high. There was a circle on the floor of small wooden blocks and as the bob reached its extreme of motion it knocked over a block. Dad was incensed. He was obsessed by accuracy and insisted that the repeated collision of the 500lb bob with a less than 1lb block had wrecked the experiment. To my total embarrassment, he loudly proclaimed that the museum curator was an idiot. Since that day I assumed that building an accurate Foucault pendulum is a difficult task and fraught with danger.

Keith_McClary, PeroK, sysprog and 1 other person
VVS2000
That's a good one!
Edit: However, building a Foucault pendulum is not a trivial undertaking and requires a large volume of lab space.
Yes. I actually played with that idea for a while and realized the hurdles

VVS2000
Build an Atwood machine, determine the moment of inertia of the pulley by timing the change in position of the known masses of the system and compare with theory.
Ok. That's some thing I can try...! Thanks

VVS2000
Build a clock based on gyroscopic precession through the rotation of the Earth.
How do I do that? You have any ideas?

sysprog
When I was a kid (pre-teen) I got to see the giant pendulum (at the Chicago Museum of Science and Industry) and I watched it for a while and started thinking about it and I became 'carsick' -- as @anorlunda hinted at (and said before I did without saying it in exactly the same way), it presents something that requires some thought to think through -- it's not all immediately obvious to us regular folks -- it seems to me that even Foucault (who was a very exceptionally bright guy) thought about it for a good long while . . .

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hmmm27
Fred Wright
How do I do that? You have any ideas?
Can you see that building a clock based on gyroscopic precession through the rotation of the Earth is the same as building a Foucault pendulum?

Gold Member
Yes, but I had in mind something based on a flywheel, which - like the FP - would try to remain in a constant orientation throughout the day,

Fred Wright
Yes, but I had in mind something based on a flywheel, which - like the FP - would try to remain in a constant orientation throughout the day,
How would you maintain the flywheel rotation without attaching a pulley to the lab frame?

Gold Member
My apologies for incorrect/misleading choice of words : precession has nothing to do with it. "Simply" attach a laser pointer to the axis mount of a gimbal-mounted (ie: freewheeling) gyroscope/flywheel.

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Homework Helper
2022 Award
I bet problem there would be to keep the flywheel spinning. Almost any motor drive will interact with the Earth's magnetic field and probably spoil the result. As will a spinning metal flywheel. But I have not done it myself...

Speaking of long pendulous objects how difficult is it to build a Cavendish balance? No air currents and a very thin torsion wire are necessary and some pretty big masses. Might be challenge.

If you just want to be amused the venerable "Newton's balls" are good. Or an hour shooting "scientific" pool. How about the magnetic pendulum to teach humility about our maths...easy to build and impossible to predict.

Merlin3189, sysprog and anorlunda
Gold Member
Just a cotton picking' minute guys. Unless the OP has an enormous laboratory store or loads of his own money then surely the biggest constraint for his decision on what to do will be what equipment does he actually have available for experiments. I know that, if I wandered around his lab store, I would find a lot of possible experiments that could be done but suggesting experiments at random to the poor guy could just prove to him that there's nothing attractive for him to do.
The Atwood machine was the only suggested way for him to go (a good idea) but it would be better if he could first give a description of the sort of gear available to him and then there would be many more possibilities.
Failing that, why not search google images for ideas (at the appropriate level)

sysprog
Gold Member
a very thin torsion wire are necessary and some pretty big masses. Might be challenge.
Certainy a challenge for a student who is not also doing practical mechanical engineering. Same problem with making one's own Newton's Cradle (i.e. using various masses). Lab technicians can be very helpful but off-the-shelf is the best sort of project to go for.

hutchphd
Gold Member
It's no wonder that students like simulations! No one knows how to use a hacksaw even, these days. The OP should get in touch with me - I just bought a milling machine and the sky's the limit, (Actually it's my ability that's the limit. )

GlenLaRocca
At the simple end of mechanical "experiments", are:

1) A demonstration of precession by holding the front wheel of a bicycle in your hands at arms length and get a friend to really get the wheel spinning, then your try to keep your hands level while you turn to the left or right.

2) Requires string, short glass tube, small known weights, and a timer. Put string thru tube, securely attach known weight, attach various other weights to "bottom", and spin the secure rate over your head fast enough to balance the bottom weight. Time a given number of spins. The bottom weight then gives you the centripetal force of the secure weight at the measured spin rates.

Gold Member
2) Requires string, short glass tube, small known weights, and a timer. Put string thru tube, securely attach known weight, attach various other weights to "bottom", and spin the secure rate over your head fast enough to balance the bottom weight. Time a given number of spins. The bottom weight then gives you the centripetal force of the secure weight at the measured spin rates.
This is an experiment that they used to inflict on KS4 kids, when I was teaching. I never quite understood how it was supposed to be run and teachers used to bully the kids into believing that it was meaningful and that they could actually get results. We had a tray of kit, as described and the kids would have a happy ten minutes, whirling the masses around, hitting each other in the face by mistake and then writing up the experiment according to the teacher's instructions. The problem is that the situation is not stable. The restoring force is Mω2r and, with any value of Weight is either too high or too low to obtain a steady value of r. The experimenter has to beat this using skill, luck and imagination. Otoh, using a Force Meter instead of the selection of hanging masses can produce a measurable relationship between restoring force, r and ω. Using a motor with variable speed gives a chance of reasonable results. In fact, a potentially good investigation.

GlenLaRocca
This is an experiment that they used to inflict on KS4 kids, when I was teaching. I never quite understood how it was supposed to be run and teachers used to bully the kids into believing that it was meaningful and that they could actually get results. We had a tray of kit, as described and the kids would have a happy ten minutes, whirling the masses around, hitting each other in the face by mistake and then writing up the experiment according to the teacher's instructions. The problem is that the situation is not stable. The restoring force is Mω2r and, with any value of Weight is either too high or too low to obtain a steady value of r. The experimenter has to beat this using skill, luck and imagination. Otoh, using a Force Meter instead of the selection of hanging masses can produce a measurable relationship between restoring force, r and ω. Using a motor with variable speed gives a chance of reasonable results. In fact, a potentially good investigation.

You can pick your weights more carefully. Did you try it yourself? Maybe 10 minutes isn't enough for the current population of students to master the hand-eye coordination required. I'd record their results and give them another 10 minutes and make it an experiment about how fast they mastered physical tasks involving their bodies. Maybe calculate the standard deviation of all groups results after 10 and 20 minutes.