# Tagged Questions

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.

45 views

### Angular momentum transfer in a bottle vortex

A colleague and I were discussing the following fluid mechanics experiment, which most people have probably tried in their kitchen: take a bottle full of water (a 2-litre transparent soda pop bottle ...
79 views

### Is there a cheap way I can do a Bell inequality experiment?

My work is almost completely theoretical/computational. But I'd really like to do a Bell inequality experiment just so I can personally see this (the best way to learn something is hands-on, right?) ...
55 views

### Layman explanation and demonstration of positive lightning

Inspired by the thunderstorm overhead, and after reading the question and answers Voltage and current of positive lightning - what is an effective means to explain this phenomenon to a layman? Also, ...
153 views

### Calculate how hot PLA will become

I am trying to attach the shaft of a brass heating tip to a PLA component. My problem is that the tip will have to reach a temperature of about 200°C and the PLA can only handle a temperature of about ...
181 views

### A good theoretical approximation for a magnetically damped pendulum

In a laboratory course we had to perform an experiment with a pendulum (just an iron weight on a wire) and play around for some time with its wire's length and so on. This was quite boring and we ...
212 views

### How can I determine the type of magnet used in a DC motor?

I repair electrical motors in a workshop and sometimes I must repair permanent magnet DC motors and other motors that use permanent magnets. I need to specify type of permanent magnet (Ferrite or ...
73 views

### Are there any tests of quantum field theory one can do using everyday objects?

One of the reasons I love physics is because many of the theories I can test using everyday objects around me. For example I can predict how long it would take for me to drop the ball of a roof using ...
20k views

### Why does cold water weigh more than hot water in a fixed volume?

Take a bucket of hot water and the other bucket of cold water. Why does the bucket full of cold water weigh more than bucket full of hot water?
164 views

### Is it possible to mix a luminescent drink? [closed]

Is it possible to create a drink that glows? In other words, is it possible to create a non-poisonous drink that fluoresces? Are there known compounds suitable for that? If not, then what about a ...
314 views

### Quantum experiments in the pre-industrial era

Could an 18th century or earlier scientist have come across phenomena which require quantum theories to explain them, given the apparatus available at the time? I'll choose 1805 as the cut-off date, ...
828 views

### Beads in 'perpetual motion'?

This page has an interesting video of beads 'syphoning' out of a glass beaker: http://blog.zennioptical.com/weekly-optical-illusion-crazy-beads/ The host has a few explanations for the effect, but ...
401 views

### Why do CD's shatter in a microwave?

Why have I heard that eggs and CD's and DVD's explode when microwaved?
833 views

### Force exerted on a cone

This is probably a pretty elemental question, but I can't figure out what the concept is called or how to calculate it. Say you have a solid cone shaped piece of ice, you hold it in your hand and ...
42 views

### How does sawdust selectively absorb water?

This Wikipedia page states that sawdust, cellulose etc. can be used to absorb water from azeotropic ethanol to produce anhydrous ethanol. How does this work? Why would the sawdust not simply absorb ...
27 views

### Does a flame put off a windlike force

When I hold a flame above a flame the one on top flickers and waves as if its about to go out. What is the cause of this?
95 views

### What makes bathroom soap bars to crack during winter season?

Is there some relation between winter season and cracking of bathroom soaps? I noticed that , cracking happens only during winter season.I also learned earlier from physics stack that, During winter ...
161 views

### About the real reason why paper doesn't fall in HALF-FILLED inverted cup [duplicate]

I just happen to see a show about air pressure host by Brian Cox. As the link:http://imgur.com/EsRadFi shows, he flipped a half-filled water cup upside down then the paper on cup doesn't drop: It ...
75 views

### Is it possible to reverse the polarity of already polarized light using passive materials?

For a gizmo idea that I have, I want to understand if it's possible to "reverse/turn" the polarity of light using passive, relatively thin and cheap films, similar to what we see in 3d glasses or TN ...
84 views

### Non-linear relationship between power supplied and perceived brightness in a filament lamp?

I was expecting the relationship between these two to be linear, but after conducting an experiment my data fits almost exactly on the curve, $y = 2800.2 x^{2.0173}$, where $y$ is the brightness in ...
224 views

### A Proposed Improvement to the Diet Coke and Mentos Experiment

I am sure most of you are aware of the Diet Coke and Mentos craze - put a few mentos in a bottle of diet coke and whoosh! Equally, I am sure most of you are aware that this occurs because the gas is ...
802 views

### Can a thrown egg chip (or break) a car windshield?

Is it possible to throw an egg with such speed that a car windshield will chip (just like with stone chips?) I have searched around for existing research in the area and have found that the impact ...
261 views

### Flipping a bottle

I tried to do this experiment recently at school and my house. I started the experiment by having three same type of bottles with the labels A,B and C. Bottle A has been fully filled with water, ...
5k views

### What happens when I place an ice cube into boiling water

My friend tried this experiment at home: She put an ice cube into boiling water. The water in the container stops boiling while the ice melts to water. My question: Why does the water stop boiling ...
807 views

### Can we create invisible things?

We are able to see this beautiful world because of light. When light gets reflected from the object, the reflected light enters our eye retina and thus we are able see that particular object from ...
668 views

### The Soda Can and air pressure experiment

Yesterday, I made an experiment. I filled an empty (but contains air) soda can with a little bit of water. Then I turn on fire at the sides of the soda can so that the water starts boiling. Next, I ...
214 views

### Motion in insulating fluid under high voltage

I observed the following phenomenon in an experiment (I'm not a student of physics, just an amateur) and was hoping for an explanation. A metal pan is electrically grounded and a layer of ...
184 views

### How to design an experiment that shows that a rectangular pulse can be expressed as a series of infinite sinusoids?

Is it possible to design a physical experiment that shows that a time limited signal, such as a rectangular pulse is composed of infinite continuous sine/cosine waves?
3k views

### Inductance - Sign convention problem…

My problem is with a circuit containing a resistor of suitable resistance $R$ and a solenoid. At time $t<0$, there was a battery that created a current in the circuit and at $t=0$, the battery is ...
553 views

### Per unit area, is there more heat transfer through the open top of a mug or the side walls?

I had a mug of hot coffee cool too rapidly for my liking the other day, which made me wonder what was the greater contributor to heat loss for a typical open-top ceramic mug: the open top, the walls, ...
84 views

### What will hapeen if we remove air from a pipe [closed]

At first i did not know if this relate to engineering or physics but i think it mostly relate for physics so i posted here. My question is what would happen if we have a pipe set vertically and have ...
110 views

### Measure ball's acceleration down inclined plane

If I am asked to devise an experiment to find an expression for the acceleration of a uniform sphere (ball bearing) rolling down an inclined plane, as a function of the angle of incline. Hence deduce ...
97 views

### Why are exploding HHO bubbles louder then pure HHO?

We tried my electrolyzer with a friend today, we filled a small bottle with HHO gas, and set it on fire. It was loud but not a big deal, like a firecracker. Then we added some soapy water and created ...
91 views

### Static electricity experiment

My teacher always asks me to do the experiments on static electricity in winter. I don't know why? What will happen if I conduct the experiment in monsoon?
839 views

### Measuring electric conductivity

My daughter is doing a science experiment on which metal (e.g., copper, silver, aluminum, iron) has maximum electric conductivity. We are assuming we can accomplish this by using different metal, 3 to ...
13k views

### If mass is added to a toy car does it affect its speed making it faster

If mass is added to a toy car (29.7g) and dropped down a wooden ramp would it affect its speed making it go faster? I know friction comes in to play to, so if you could give me an answer or an ...
919 views

### Heat absorbed by a room

How can one calculate the amount of heat absorbed inside a room in a single day using the temperature readings of the day? If the temperature has to be reduced from 30C to 20C how much heat should be ...
34 views

### Can vernier scale ratio be less than 1?

I came across a question (See Image) that states about two vernier scales The first vernier scale is the top-most figure in the image: It has 10 vernier scale division equal to 9 main scale division ...
69 views

### How to measure the mass and balance point of a human forearm?

I've been trying to find this out for about a month now. I'm usually met with humorous but not really helpful comments about chopping my own arm off. I'm preferably looking to do this on a budget ...
48 views

### Creating airflow in a mini greenhouse [closed]

How do I create the best airflow for a mini victorian style greenhouse, that has a total volume of 80148.75 cm3? I leave the lid on top, which is a triangular prism in structure, open about 2.54 cm. I ...
168 views

### Will my induction hob be powerful enough? [closed]

I'm looking to buy an induction hob to heat some water and I would like to know if its going to be powerful enough. If so, can it be done in, say, 1 hour? Additionally, what power rating could I go ...
106 views

### Why covering our nose with a cloth or nose mask reduces stale smell?

Whenever there is a stale smell in air, we tend to use a cloth(maybe a handkerchief) instantly to get away with it. Why does a cloth or a mask reduce the intensity of a stale smell? Are the "smell" ...
43 views

### Experiment Equipment Supplier (for use in the Classroom & at Home) [closed]

Does anyone know of an online store that sells equipment specifically designed for carrying out demos in the classroom or at home? I'm helping out a student taking college physics and chemistry. These ...
69 views

### Ideas for improvised UV filter

I am doing a project where I would like to do some UV exposure to some concrete and stone samples. Therefore I have bought a couple of 400 watt UV bulbs, the product specification says it has an ...
661 views

### Do different density objects in liquids affect net weight [duplicate]

I would test this but I have no tools to test it with. If I have a beaker of water and weigh it on a measure. Then I stick my fingers in the water (it doesn't over flow) does the weight change or ...
563 views

### How much power you might need to generate dangerous EMP shock?

While playing with voltage multiplication and capacitors, I began to think if my experiments could damage my electrical equipment (eg. mobile phone) by creating strong magnetic fields over a short ...
211 views

### Conservation of energy and the 'crazy ball' product

Well I'm not sure how many people remember the crazy ball - a small ball made of rubber which bounced like crazy. What I noticed is that the ball seemed to bounce higher than the point from which it ...
2k views

### Experiment - Measuring final velocity of a parachute

I'm working on a project that involves a scale parachute. It is vital for the project to get a good measurement of the speed it has when it lands. We still haven't built the parachute, but we need a ...
120 views

### The best way to cool the teapot

My professor today in the class made us a question: "Lets say we have a teapot with water in it.The water is hot.Now we want to cool the water. Will it cool faster if we put an ice cube above the ...