emma123321

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Blog Entries posted by emma123321

Here on earth we are so used to seeing heavier objects fall faster than lighter objects; if I were to drop a bowling ball and a piece of paper at the same time, it is pretty obvious that they would fall at different rates. The paper has a small mass compared to it's surface area, and the bowling ball has a larger mass compared to its surface area. It takes longer for the piece of paper to push away the air molecules, than the bowling ball.

So how come on the moon, a feather and a hammer fall at the same speed?

It has a lot to do with air resistance! Air resistance is the action of friction that slows something moving through air.

A vacuum surrounds the moon, and there is no matter in a vacuum. Therefore, on the moon there is no air resistance. So when Commander David Scott dropped the hammer and feather on the moon, the moon's gravity pulled both the hammer and the feather in at the same rate of acceleration. Because there is no air resistance to slow down the fall, the two objects fall at the same rate.

In the video posted below, Commander David Scott drops a hammer and a feather on the moon! Its an amazing video and thanks to physics, I understand how this is possible!

Today, while looking in the mirror, I suddenly became very curious as to how mirrors work. I remember talking about mirrors in physics class, especially when talking about reflection, but there is even more to it!

The first thing I learned is that there are three types of mirrors: plane, convex, and concave. I will talk about plane mirrors. With plane mirrors, the image is always upright, virtual, and the same size.

The Law of Reflection is a huge part of how plane mirrors work. This law states that when light falls upon a plane surfave, it is reflected so that the angle of reflection is equal to the angle of incidence. This only happens when the reflected ray and the normal ray both lie in the plane of incidence.

This law applies to mirrors because when light falls upon a plane surface, or a mirror, it is reflected, and the angle of incidence and the angle of reflection are equal. When the eyes recieve the reflected light waves, it looks as if the waves are diverging from behind the mirror. This specific type of image is called a virtual image. The light waves don't really pass through that point it only looks as if it does.

This image shows how the reflected angle is equal to the angle of incidence.

Hopefully this provides a little introduction to mirrors, there is certainly a ton more information about how mirrors are related to physics!

This is completely random, but as I was pondering ideas for a blog I discovered that there is a lot of physics involved in toasters!

Most appliances that heat up, such as hair dryers, irons, and toasters, work by changing electrical energy into heat energy. Toasters are plugged into a source of electricity. From that source, the electric current runs down the wire and into the toaster. The inside of each appliance contains loops of different metals. The electricity does not easily flow through the metals. The metals slow down the electrons and hold up the current, which is resistance. Resistance is a measure of the tendency of a material to resist the flow of an electrical current, in physics. The higher the resistance, the hotter the metal will get. This happens because of the friction of the electrons.

The wires begin to heat up and glow because they are so hot. This heat is what toasts the bread.

Overall this is very random, but its cool to see how everyday appliances like toasters relates to physics!
Did you know that when a dog's sense of hearing fully develops, it can hear about four times the distance of a human with normal hearing? How is this possible?! Well, it actually has a lot to do with physics.....

Humans can typically hear sounds from within the frequencies of 20 Hz and 20,000 Hz, meaning they usually can't hear any sounds below the frequency of 20 Hz or anything above the frequency 20,000 Hz. Frequencies that are out of the range of human hearing are untrasonic (cyclic sound pressure with a frequency greater than the upper limit of human hearing) On the other hand, dogs can typically hear sounds with frequencies approximately 40Hz to 60,000 Hz. Frequency in this case is the number of sound pressure level vibrations (sonic waves) per second.

Although a dog's hearing capability is dependant on its breed, there are some distinct reasons why dogs hear better than humans. First, when dogs hear a noise, they move their ears towards the sound in order to maximize the reception (they have at least 18 muscles in their ear that allows the ear to tilt and rotate). By doing this the sound waves are more easily directed into the ear.

This may be why vacuum cleaners often scare dogs away. The vaccuum, and other sounds that are loud to humans often emit high frequency tones that scare away dogs. This video below further discusses frequency and the range of sound humans can hear vs. dogs.
Have you ever been curious as to how a balloon can magically stick to a wall after rubbing it against some sort of material? This happens because of Static Electricity.

Static Electricity is a familiar electric phenomenon in which charged particles are transferred from one body to another. When you rub your hair or a sweater against a balloon, charge transfer occurs, and Static Electricity is produced. In simpler terms, if you rub a balloon against your sweater, the balloon will steal electrons from the sweater, which leaves the sweater positively charged and the balloon negatively charged. The balloon will most likely be attracted back to the sweater because opposite charges attract. The reason that the balloon will stick to the wall is because the negative charges in the balloon will make the electrons in the wall move to the other side of their atoms (like charges repel) and this leaves the surface of the wall positively charged. Because opposite charges attract, the negatively charged ballon will be attracted to the positively charged surface of the wall.

Something interesting that I stumbled upon while doing this research was some different materials that cause a lot of static electricity are rabbit fur, human hair, cat fur, glass, and dry human skin!

http://phet.colorado.edu/en/simulation/balloons <------- This website has a great simulation that shows more of how Static Electricity works, I know when I first learned about static electricity, this simulation helped me to visualize how it works.
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