Centripetal & Centrifugal
What do centripetal forces and centrifugal forces do?
Centripetal force moves us towards the center. Gravitation is an example of centripetal force. Centrifugal force moves us away from the center. The thrust created by a rocket engine is an example of centrifugal force. To take the example one step further, rockets manage to escape the Earth's gravitational pull (centripetal force) by creating a greater counteracting thrust (centrifugal force).
Evolution of dogs
Did all of the different breeds of dogs start with one dog?
Yes. Evolutionarily, all dogs began as wolves. They evolved somewhat on their own into slightly different breeds based on location and variation, but really began to develop into the breeds we know today when they were domesticated by humans and certain traits became desirable to different people. This is also why many purebreds have health problems; they were bred to have features unnatural to them, and now they are suffering for it.
Mass and weight
What is the difference between mass and weight?
It might be better to say that mass is the amount of "stuff" inside an object measured in kilograms. While increasing the size of an object can increase its mass, two objects of the same size can have different masses, depending on their density. To understand the difference between weight and mass, think about traveling to different planets. On each new planet, your weight (measured in Newtons) will be different because the gravitational force is different, but your mass will always be the same (provided you don't go to the bathroom or get a haircut).
Where did "roger that" come from and what does it mean?
ROGER -- "in the meaning of 'Yes, O.K., I understand you -- is voice code for the letter R. It is part of the 'Able, Baker, Charlie' code known and used by all radiophone operators in the services. From the earliest days of wireless communication, the Morse code letter R (dit-dah-dit) has been used to indicate 'O.K. -- understood.' So 'Roger' was the logical voice-phone equivalent." "Morris Dictionary of Word and Phrase Origins" by William and Mary Morris (HarperCollins, New York, 1977, 1988).
Adopting healthy pets
Are pets that you adopt as good and healthy as pets from a pet store? I think it's the right thing to do to adopt, but I don't have a whole lot of money and want to make sure the pet I adopt won't be in and out of the vet.
If you adopt a pet from your local animal shelter the animal should have already been vet checked! No animal shelter adopts out sick or unhealthy pets as a general rule. Of course, there are exceptions, so ask! Just remember, all pets, whether from the shelter or the store, just like children, need regular doctor check-ups, vaccinations, and more. You can give the vaccinations yourself if you are comfortable with the idea (I do and it isn't that difficult). Besides, if you don't have a lot of money (gee, who does) your local animal shelter's adoption fees will cost a lot less than purchasing a pet from a pet store and you will be saving a life to boot!
I can't take the pressure!
Why don't fish get crushed from the pressure deep in the ocean?
Because the pressure inside their bodies is about equal to the water pressure outside their bodies. This is precisely the reason why each individual species of fish is limited to a very specific range of depths. Should the fish venture too deep, the pressures of the overhead water will indeed crush him. Should he venture too shallow, his internal body pressure will exceed that of its surroundings and he will (quite literally) explode. I should add that it would be possible for a fish to move into a depth range that is outside his normal sphere. The fish would have to do so very gradually, however, to give his body time to equalize the pressure difference.
How is gravity different in space than on earth?
The effects of gravity (i.e. your weight) depend upon your proximity to a massive object. As you move away from the Earth, its gravitation affects you less (i.e. your weight decreases). If you were to move close to the Sun or Jupiter, your weight would increase beyond its Earthly value because both objects are more massive than Earth is. In deep space, you will generally weigh very little or nothing because of your distance from massive bodies.
Why are there variations?
There is a variation in nature, distribution, and forms of marine sediments all over the world (both vertically and horizontally). What are the various ways climate contributes to the variations and what are the results?
Sea levels rise and fall over geological eons. Earth movements lift areas that were originally under the sea, so marine sediments no longer accumulate. In terms of climate, some areas will be wetter, with more water bringing more sediment into the sea and other areas will be drier, so less sediment is brought down. Also, the type of land through which water travels will affect the type of sediment deposited.
What is cache?
Pronounced cash, a special high-speed storage mechanism. It can be either a reserved section of main memory or an independent high-speed storage device. Two types of caching are commonly used in personal computers: memory caching and disk caching. More info here: http://www.webopedia.com/TERM/c/cache.html.
How heavy is your brain?
What is the weight of the human brain?
The human brain will obviously vary between people but it is around 1.5kg (3lbs) (80% of which is water). On average, a woman's brain is 200g (7oz) lighter than a man's; this is due to the fact that men, on average, have bigger heads.
Transferring MP3 files
How do you put songs onto an MP3 player?
Are you speaking of a portable or computer-based player? Usually, for portable devices, you plug the device into your computer and copy songs over with the program that came with it. When it comes to computer-based players, you can usually locate MP3 files and drag them over into the player like you drag files to new folders or the recycle bin.
Arthritis & Rheumatism
What is the difference between arthritis and rheumatism?
They both cause degeneration in the weight-bearing joints, but rheumatoid arthritis results from the body attacking itself, causing bony deformities. The other arthritis, or osteoarthritis, is due to degeneration of the cartilage and connective tissues, allowing bone on bone, which causes the break down of the joint and pain.
How is a nation paid for sending and receiving foreign mail?
The postal service of each nation is responsible to pay for the delivery of a letter/package to the target nation's frontier (e.g. airport). Secondly, each nation's postal service is responsible to collect letters/packages from all post boxes, post offices, frontier points, etc. Finally, it is also responsible to deliver all letters/packages destined for a point within its borders, regardless of the collection point (which may be a frontier point). In other words, postal services do not get reimbursed by other countries. They must subsidize their responsibilities themselves (i.e. primarily stamp sales).