by Ron Kurtus
Readers have sent in a total of 4977 comments and questions on Science issues. They are listed according to date.
You can read them to further your understanding of the subject.
|Sound reflecting off barriers||Sound and Obstacles||Australia|
|First grade science fair project||Magnetic Materials||Senegal|
|Voltage and frequency used in europe?||AC World Voltages||India|
|Can't find sound waves quiz||Sound Waves||USA|
|Correction on exponent||Force Between Two Objects||UK|
|Frequency when reducing length by 1/2||Pendulum Equations||Pakistan|
|Object on a ramp||Friction on Inclined Surface||USA|
|Will different surfaces affect speed?||Force Affects Motion||Jordan|
|Studying for GED in science||General||USA|
|Plugs on appliances from 1950 get hot||AC World Voltages||USA|
|Will induction motor from Japan work OK?||AC World Voltages||USA|
|Where is friction not needed?||Uses of Friction||Swaziland|
|Does density of fabric reduce echoes?||Sound and Obstacles||Saudi Arabia|
|Will static electricity attract fibers in home?||Uses for Static Electricity||USA|
|Thinks gravity causes friction||Causes of Friction||India|
Sound reflecting off barriers
March 1, 2016
Hi, my questions are as follws:
1. What barriers does sound reflect off?
2. Why does sound reflect off barriers?
3. Is the surface that the wave reflects off affecting the length off the wave?
Thank you for your time!
Sophie - Australia (26824)
Sound will reflect off any solid barrier, although some sound may be transmitted through the barrier and some may be absorbed. Sound can also be reflected off a "barrier" of a liquid or even some gas.
Sound is a series of compression waves where molecules move a short distance, causing the next group to move. If there is a barrier, the wave of molecules would bounce off in the other direction.
The only time the length of the wave (wavelength) changes on reflection is if the barrier is moving, causing the Doppler Effect.
First grade science fair project
March 1, 2016
I work on magnetism for first grade science fair how to win?
faty - Senegal (26825)
Your goal in the science fair should be to do your best to show others about magnetism as well as to do an excellent job.
You can demonstrated or show some effects of magnetism. See Magnetism Project: Make an Electromagnet for an example.
Note that it is important to have a display or some sort that others can see.
Best wishes on doing a great job in your project. I am sure you will.
Voltage and frequency used in europe?
March 1, 2016
how much voltage and frequency used in europe? please Answer me as soon as..... possible
Bharathi - India (26828)
Most countries use 230V and 50Hz.
See List of Worldwide AC Voltages and Frequencies for values in various countries.
Can't find sound waves quiz
February 25, 2016
i cant find the quiz anywhere plz help seriously
- USA (26806)
You can click on the Mini-Quiz tab at near the top of the page for a short quiz on the subject. Also, there is a larger Graded Physics Test on Sound Waves that you can access.
I hope that helps.
Correction on exponent
February 25, 2016
Hi, Great site, but your page with the calc of the gravitational force between two people is wrong at the end when you convert to standard scientific notation. It should be 0.9x10-6, not -16
- UK (26809)
Thanks for pointing that out to me. I made a goof on handling the exponents. I corrected the Gravitational Force Between Two Objects page.
Frequency when reducing length by 1/2
February 25, 2016
What will be the frequency of simple pendulen if its lenght is l/2
muhammad - Pakistan (26810)
The frequency equation is: f =[?(g/L)]/2?. If the length is reduced by 1/2, the frequency will increase by the square root of 2 or 1.414
Object on a ramp
February 24, 2016
A 65.0 kg object is sitting on a 32.0 degres.The coefficient of friction present is .540.(Assume it will move down the incline).What are the values of the(a)WEIGHT force,(b)Normal force,(c)Parallel force,and the(d)Friction force?
Franck-Alain - USA (26805)
The normal force pushing the object to the surface of the ramp is N = mgcos(a), where m = 65 kg, g = 9.8 m/s^2 and the angle (a) is 32.
The resistance due to friction is Fr = Nfr, where fr = 0.54.
You can do the calculations.
Will different surfaces affect speed?
February 21, 2016
will different surfaces affect a speed of an object??
leen - Jordan (26798)
If an object is sliding along a surface, the amount of friction between the two surfaces will affect the speed. A rough surface will usually have more friction resistance than a smooth surface and thus slow down the speed of the object more.
See Resistive Force of Friction for more information.
Studying for GED in science
February 21, 2016
Im studying for my GED and i need help in science? Can you send me information to help me understand snd pass my test?
Kendria - USA (26799)
You can go through the various lessons in the areas of Physical Science to help you understand the subjects. The GED tests may be on Physics, Astronomy, or Chemistry. You can study lessons in each section, according to the tests you are taking.
There are websites that give practice GED tests. See GED Science practice test and GED science as examples. They should help.
Best wishes in doing well in your GED. I am sure you will excel.
Plugs on appliances from 1950 get hot
February 20, 2016
I have several appliances that had belonged to my grandmother. They are all from the 1950s. (A deep fryer, waffle maker and sewing machine). In the states their plugins seem to get hot and I have to be careful to not get shocked when unplugging them. For a while now, I have lived in Asia, and these appliances seem to work better.
My question is, were the older appliances made to be on a different voltage or Hz? Is it just coincidence? I wonder when I return to the states if a converter is necessary for them to work their best or not.
- USA (26796)
Appliances meant to run on 50 Hz will run slightly warmer on 60 Hz.
However, electrical appliances that are over 60 years old have gone well past their useful life. Not only do they take more current than newer models but there is also the risk of wires shorting out and causing problems.
If the plugs seem hot, that is a warning sign to you. It would be est to start thinking of replacing those appliances.
Will induction motor from Japan work OK?
February 18, 2016
I have acquired an induction motor from Japan whose data plate says: 100V 60hz 0.48a, single phase, 25W with a 7.0 uF capacitor.
Can this be safely used without a transformer on regular 110v 60hz US household current?
Scott - USA (26790)
The motor will run a little hotter with a 10% higher U.S. voltage. In general, that would not be a problem with only 25W power.
However, just to make sure, you could check with the company.
Where is friction not needed?
February 16, 2016
where is friction not needed?
siboniso - Swaziland (26787)
Friction is not needed if you do not want to stop or slow down a moving object.
Does density of fabric reduce echoes?
February 15, 2016
PLEASE I WANT TO KNOW IF THE DENSITY OF THE FABRIC REDUCE THE ECHO MORE THE FABRIC IS DENS IT MEANS WILL ABSORB BETTER THE ECHO....THANKS
Moh'd Jamal - Saudi Arabia (26782)
Heavy drapes over a window helps to reduce outside sound much better than thin curtains. Now to reduce an echo, many concert halls used to use a heavy fabric on the walls to absorb the sound. However, these days most use sound absorbing wall and ceiling materials. But I don't think they do as good of a job.
You don't want the fabric to be so dense that it is almost hard. Then it would actually do little to reduce the echo. You want the sound to travel into the spaces in the fabric and then get absorbed.
I hope that helps.
Will static electricity attract fibers in home?
February 7, 2016
We had an unfortunate occurrence happen in our mobile home. A couple of heat registers came loose from the main trunk line causing underbelly insulation fibers to be sucked up and throughout our home. These fibers are everywhere. One member of our family has been to the Doctor three times and the Emergency Room once. Fibers are embedded into her feet, hands and eye. Doctors do not have a solution or remedy. We do have a cleaning crew scheduled to clean our home in a couple of days. They will use an industrial vacuum cleaner with a three stage HEPA filter to suck the insulation fibers out. My question is this: Could static electricity potentially attract all the fibers to clean our home? You can feel them cling to your body as you are walking through the home. How or what would we use to generate enough static electricity to be effective?
Jim - USA (26761)
Sorry to hear about your problem. High power vacuuming should get out most of the fibers. But there probably will still be some stubborn ones in crevices and such.
Static electricity would attract many of the fibers. The problem is getting a device that would create the static electricity and then move around to attract the fibers.
Note that your bedding, clothes, and other fabrics probably need to be cleaned to get rid of any fibers embedded in them.
Best wishes for cleaning up this nasty problem.
Thinks gravity causes friction
February 2, 2016
the main causes of friction is gravity present in earth. And i have full explanation of it but you should believe on me.
Abhishek - India (26741)
There is friction when you slide an object along the ground of other surface. The Earth's gravity causes the object to have weight and pulls it toward the other surface. The sliding of the surfaces results in the friction.
Gravity does not cause the friction but contributes to the effect. The friction in the brakes of a car have nothing to do with gravity.
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