questions concerning measurements, experiments, and activities that demonstrate physics and are safe to do at home, require at most one tool or ingredient not readily available, and can be interpreted or analyzed on one sheet of paper with accessible math.
161
votes
19answers
55k views
Cooling a cup of coffee with help of a spoon
During the breakfast with my colleagues, a question popped into my head:
What is the fastest method to cool a cup of coffee, if your only available instrument is a spoon?
A qualitative answer would ...
28
votes
13answers
7k views
Home experiments to derive the speed of light?
Are there any experiments I can do to derive the speed of light with only common household tools?
22
votes
6answers
2k views
How do whisky stones keep your drink cold?
From a discussion in the DMZ (security stack exchange's chat room - a place where food and drink are important topics) we began to question the difference between how ice and whisky stones work to ...
21
votes
2answers
417 views
Why does laser light not affect glowing materials?
I have this childrens rubber ball which glows in the dark after it's exposed to light. I "charge" it with a flash light then play with my dogs at night. I thought to try a very intense green laser, ...
21
votes
1answer
693 views
Energy in bolognese reduction - lid on or off?
Generally, to let my bolognese thicken, I leave the lid off in order to "let water vapor escape." I am however distracted from enjoying the taste because I'm having doubts that my physical reasoning ...
17
votes
3answers
5k views
Why does the water rise?
It's a very popular experiment (eg), from elementary school : put a burning candle on a dish filled with water, cover the candle with an inverted glass: after a little while, the candle flame goes ...
16
votes
3answers
1k views
Why does the sound pitch increase on every consecutive tick at the bottom of a filled cup of coffee?
Since I don't know the proper physical terms for this, I describe it in everyday English. The following has kept me wondering for quite some time and so far I haven't found a reasonable explanation.
...
15
votes
2answers
404 views
Why does the note played by a flute not change in this case when the air column is interrupted?
I play the flute as a hobby, and I've noticed that when playing middle D or E flat, one can interrupt the air column by releasing a certain key (which is near the middle of the air column), and yet ...
13
votes
3answers
1k views
Home experiment to estimate Avogadro's number?
How to get an approximation of Avogadro or Boltzmann constant through experimental means accessible by an hobbyist ?
12
votes
9answers
912 views
What are good mechanics experiments for 10 year olds?
I'm trying to explain elementary mechanics - without the benefits of calculus or even algebra - and struggling. I'd like to find reasonable ways to demonstrate Newton's laws, minimally, and possibly ...
11
votes
4answers
1k views
How can I measure the mass of the earth at home?
How can I measure the mass of the earth at home?
How was the mass of the earth first measured?
11
votes
1answer
1k views
Home experiments to measure the RPM of a pedestal fan without special equipment?
Is it possible to determine to an approximate degree, the revolutions per minute of a fan, for example a pedesal fan pictured below, without using some electronic/mechanical measuring device?
One ...
11
votes
2answers
2k views
Why do grapes in a microwave produce plasma?
Some of you may know this experience (Grape + Microwave = Plasma video link):
take a grape that you almost split in two parts, letting just a tiny piece of skin making a link between each half-part.
...
11
votes
3answers
1k views
How does paper make sound when it is torn?
We know that from our experience when we tear up a piece of paper, we can hear a characteristic sound. What is the underlying mechanism behind it? What do the dominant frequencies (edit: I don't mean ...
11
votes
6answers
1k views
Tried to do the double slit experiment, failed. Why?
I tried, and failed, to do the double-slit experiment. I thought I had a good experiment setup, but obviously I was wrong. Can anyone offer some insight in what I might have done wrong? Most of ...
9
votes
7answers
3k views
Why is a 1mW laser dangerous?
In our Physics lab we have a 1 milliwatt (0.001W) helium neon laser. Despite the low power, we were cautioned not to even look at reflections of the beam as it could cause permanent eye damage - why ...
9
votes
6answers
844 views
Simple Experiment to Demonstrate Special Relativity
I am trying to think of a good experiment that can be done for under $250 or so that would demonstrate some aspect of Special Relativity. Ideally this will be done in a few years with my kids when ...
8
votes
3answers
528 views
How hot is the water in the pot?
Question: How hot is the water in the pot? More precisely speaking, how can I get a temperature of the water as a function of time a priori?
Background & My attempt: Recently I started spend ...
8
votes
4answers
757 views
What happens when you heat vodka in a microwave?
Since ethanol has a lower dielectric constant than water would the water heat up and boil before the ethanol? Would the water transfer heat to the ethanol and, since ethanol has a lower boiling point, ...
8
votes
3answers
700 views
Is it possible to reproduce Double-slit experiment by myself at home?
I want to reproduce this experiment by myself. What I need for this. What parameters of slits and laser/another light source it needs? Is it possible to make DIY-detector?
8
votes
1answer
81 views
Where can I find information for how to create amateur radio telescope?
Where can I find good source of information for how to create amateur radio telescope.
Particularly interested in creating Fresnel Zone Plate Antennas (aka flat dish).
design, diagrams, ...
8
votes
2answers
751 views
The Galileo thermometer: why do the bubbles float in the middle of the tube?
If the water were uniform temperature, it would have uniform density, so a bubble should either be all the way at the top (if it's lighter than water) or all the way at the bottom (if heavier). But in ...
7
votes
1answer
502 views
Why does the water in the toilet move around so much on stormy days?
On calm days, the water in the toilet looks completely still. But when it's rainy and windy out, the water looks like it moves and pulsates. Why is this?
7
votes
1answer
570 views
What are the specific requirements for a do-it-yourself quantum double-slit experiment?
I was shocked to recently learn that the double-slit experiment is not only possible to do with completely ordinary equipment (with photons of course), but it actually looks rather easy. This is from ...
6
votes
3answers
3k views
Why do lightbulbs continue to glow after the light is turned off?
I've noticed that whenever I turn the lamp off in my room at night, the lightbulb seems to continue to glow for a minute or so after that. It's not bright though; the only way I even notice it is if ...
6
votes
2answers
3k views
Does tea stay hotter with the milk in it?
A little thought experiment, similar to this one: Imagine you are making a cup of tea when the door bell rings. You've poured the boiling water into a cup with a teabag in it. As you're just about to ...
6
votes
2answers
828 views
How to count photons
How are photons counted?
What is the experimental setup used to count photons from a laser or even a lamp? Of course, in the case of the lamp, I would be able to count only the photons that pass ...
6
votes
2answers
123 views
Must a vertical sundial face exactly South?
I am a sundial. I'm prepared to bet
Your watch can't tell when the sun will set
I once heard Frank King talk about sundials in particular this very cool one, which measures Babylonian hours ...
5
votes
8answers
427 views
Example of a time varying function which can be easily measured
My sister is in 10th grade. She doesn't seem to understand the concept of time varying functions (current, light, sound wave forms etc). I explained her in easiest possible terms. She got it but not ...
5
votes
4answers
543 views
Astronomy Experiments for Amateurs
Are there any resources online for astronomy experiments that I can perform myself?
I am looking if anyone knows any measurements to take while looking for various objects during the evening ...
5
votes
2answers
763 views
Black hole analog experiment?
This question is directed mostly at people giving lectures on black holes, but input by other physicists or students is very much appreciated.
Do you know a good (home)-experiment with a black hole ...
5
votes
1answer
225 views
Are coffee's properties different enough from water's to cause increased spillage while walking?
I recently found this article, which describes how...
It just so happens that the human stride has almost exactly the right frequency to drive the natural oscillations of coffee, when the fluid is ...
5
votes
3answers
226 views
How can I determine the coefficient $k$ in $ \dfrac{dT}{dt} = -k(T - 100 \mathrm{^\circ C}) $?
I recently spend some time on cooking and I'm curious about the time evolution of the temperature of the water. I did some experiment and the temperature is of the form
$$ T = 100 \mathrm{^\circ C} + ...
5
votes
2answers
514 views
What are insightful/impressive experiments for adults
Similar to this question: what experiements do you think are impressive for layman adults?
I for example like how you can simulate an Einstein Ring with the bottom of a wine glass.
5
votes
1answer
91 views
Whistling on bottle tops
It is well known that if you blow horizontally on a bottle top it creates a sound. Pouring water to the bottle changes the pitch.
I have been doing experiments on the relation between the sound's ...
5
votes
1answer
134 views
Practical method to weigh human limbs with common household items?
What methods could be used to determine (or estimate within a reasonable margin of error) the mass of a living human's limbs, short of cutting them off? And more interestingly, how can this be done ...
5
votes
3answers
1k views
Rough, easy DIY method of measuring magnetic field strength
How to easily, using standard DIY equipment measure the strength of magnetic field generated by a permanent magnet?
Narrowing down the "loose language" of the above:
strength of magnetic field: ...
5
votes
2answers
113 views
Is it cheaper to boil water on high gas heat or low gas heat?
Assume my time value is \$0. High gas heat adds more energy per second to the water but the pot may absorb the heat less efficiently, or maybe the shape of the flame is less good, or for other reasons ...
4
votes
3answers
1k views
Why does hot oil explode when pouring water on it?
I am puzzled to know, What is the reason of hot oil make sound and explode when we pouring water on it?
4
votes
1answer
96 views
Physics of every-day life: rotating bag of tea
Whilst studying for my physics courses, I like to drink tea. Today, I noticed that if you pull a bag of tea out of a hot cup of water, it gradually starts to rotate, picking up speed as time ...
4
votes
1answer
111 views
How can there be a path to ground with thick shoes and a carpet?
I'm connecting a test light to one pin of an halogen lamp. When I touch the metallic part on the back of the test light, the light glows, as it is supposed to. However, I have thick shoes and I am ...
4
votes
4answers
226 views
Applications of recoil principle in classical physics
Are there any interesting, important or (for the non physicist) astonishing examples where the recoil principle (as special case of conservation of linear momentum) is applied beside rockets and guns?
...
4
votes
2answers
139 views
What are the lines visible between two cards held edge-to-edge?
Hold two cards (say credit cards) edge to edge, anything from a very slight
touch to about 1/3 mm separation, in front of any ordinary light
source. When I do this I see several
fine dark parallel ...
4
votes
2answers
67 views
Is it viable or possible to make your own transistor?
Just wondering if it is possible/viable to construct your own transistor, not small like todays, but the same scale as the one created at Bell Labs.
4
votes
1answer
72 views
Can I find the frequency generated by tapping a battery on a coin?
According To How Stuff Works , if you tap a 9 volt battery on a coin it will transmit Radio waves. I was wondering, because I don't have a radio with me at the moment, Is there a way I could discover ...
4
votes
4answers
396 views
How would you design an experiment to grok optical phenomena?
I've been toying with the idea of making a 3D scanner that uses an IR distance sensor to find position vectors of an object in space and then translates that into a 3D computer model.
One of the ...
4
votes
2answers
116 views
Room temperature and fan orientation
So I'm in a tiny dorm room and I normally point my fan blowing outside the window to cool my room off. I've been in some debates on blowing air out or in is more effective, so I'm hoping to get some ...
4
votes
2answers
660 views
Is a given volume of sparkling water lighter or heavier than the same volume of still water?
I can see it two ways - if all the $CO_2$ has turned into bubbles I would imagine it is lighter. However dissolved $CO_2$ atoms are probably heaver than the $H_2O$ atoms they replace, or fit in ...
4
votes
0answers
122 views
Why does the milk frother on my coffee machine make so much noise?
I have a Sunbeam home espresso machine with a steam wand. The steam roars out straight from the end of the wand. When it's first placed in the cold milk it really screams! Once the milk has a bit of a ...
4
votes
0answers
85 views
Handling halogen lamps
When consulting manuals, electricians, online sources, etc., they always instruct you to handle halogen light bulbs with gloves.
The "explanation" that usually accompanies this statement is that oils ...
