# prettybird

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1. ## Force on a Nail

Hanging a picture can actually show a lot of physics dealing with force and friction. First, you have to hit the nail with a hammer into the wall. Each time you hit the nail, you have to overcome the force of friction between the wall and the nail to get it to go in further. The hammer rebounds back after hitting the nail and you feel the force in your hand. Then, depending on how heavy the picture you hang is, the wall has to exert a force equal to m*g on the nail to overcome the combined weight of the picture and the nail. If it exerted a force less than mg, the nail and picture would slide down the wall, leaving you with a large crack. Any larger than mg and it would accelerate upwards. If you have two nails, the picture can be better supported because the wall can split the same force between two, so for a heavier picture use more nails.
2. ## Opening up a Laptop

One equation in physics is torque, which is the Force applied to object to rotate it about an axis times the radius the force is applied at. Torque only takes into account the force perpendicular to a surface, because any other direction will not cause it to spin. When you open up a laptop, either with a force at some angle or directly perpendicular, the force acting perpendicular causes a net torque and spins it about the axis. The same can be seen on doors, and even books. Also, some caps that come on hinges, like a lotion bottle, can be described in this way. As long as some of the force is directly perpendicular, the surface will move in the way it is being pushed or pulled.
3. ## Machine Guns and Rollerblades

I had an incredibly weird dream the other night. I was driving with my mother and in front of us was a man on roller blades using two machine guns taped to his arms to propel himself forwards. I was about to forget my dream all together until I started thinking if physics would allow such a thing to happen. Similar to the way a rifle would recoil when a bullet is shot, the machine guns would recoil when the bullets are shot out of them. Normally, they are anchored to something so the recoil is hard to notice. However, the force exerted on the machine gun would then be exerted on the man, whose body would normally compensate and return the machine gun to its original position eventually. Since he is on rollerblades with little or no friction (it's my dream, I'm neglecting friction), the force would propel him forwards. And since he was firing them at a rapid rate, this would in turn propel him forwards at a decent speed. So, while this is an entirely reckless, irresponsible and dangerous idea, it is physically possible to achieve.
4. ## Physics of a Grandfather Clock

I used to wonder why the pendulum in a grandfather clock was there, and I originally thought it was for purely visual interest. Now, I realize that the pendulum acts as a pendulum to keep the clock working at exactly the right time. The pendulum has a period of 1 second and each time it swings left or right, it moves the clock through one second. But what length should the pendulum be in order to keep time at 1 second? The equation for the period of a pendulum is T = (2* pi) (L/g)^(1/2) and when plugging in the value of 1 s for T and 9.81 m/s for g, you get that the length of a pendulum to keep time correctly is about .25 meters.
5. ## Stardew Valley

One of my more recent favorite games has been Stardew Valley. It is essentially an updated version of the game Harvest Moon, which originally came out in 1997 on the Gameboy, which is what I originally played it on. It is a game where you inherit a farm from a dying relative, and you come to find it overrun with weeds, trees and rocks. You slowly clear it out, plant crops and adopt animals. You can also mine and fish, and you slowly build relationships with the people in the town by joining them at festivals or bringing them gifts. You also have the opportunity to start a family. For the most part, the game seems fairly realistic. You have to bait your fishing rod, it takes alot of hits to chop down a tree and you lose energy the more you preform a task. However, the mine introduces something that really breaks physics in this game. The first mine you journey into have 120 floors, and when you reach the bottom you receive a skeleton key. Once you unlock the desert, you have the chance to open another endless mine Two things here are the problem. One, this mine is truly endless, and at some point you would not be able to go any farther because you would hit the center of the earth and just burn up. Also, you can find holes which allow you to drop down levels. Not a ladder, like how you progress most of the game. It is a literal hole you must jump down. I have seen someone jump down 11 floors at one time. Now, it does take away some health, but assuming that each floor in the mine is around 6 meters minimum, you would fall 66 m, meaning you would be falling at around 36 m/s by the end of your fall. This would surely cause a bone to break, but you come away unscathed.

7. ## Surface Tension of Water

I've heard the same principle (sort of) applies to those who lay down a bed of nails. Their weight is spread over so many nails that there is very little force on each nail.
8. ## Waffles are the best

Pancakes are way better, the softer surface is more porous, allowing syrup and butter to soak into it and fill it with flavor.
9. ## The Grand Tour

That must have taken a lot of work, I'm glad they were more precise than we were in the lab we failed at in class last quarter.
10. ## The Death Star

A real Death Star would probably also affect our moon's orbit, which would then affect the tides and water levels on Earth.
11. ## PaVG #11: Ground Pound

How much force do you think it would actually take to move the ground the way some of the "ground pounds" are displayed in some video games?
12. ## PaVG #14: Overwatch

Do you think it would ever be possible to have a small weapon harnessing sound in real life? That would be a cool weapon to see in action.
13. ## Electric Charge and my Cat

In the winter time it seems that everyone is shocking each other. I shock myself on every chair at school, I swear. The worst feeling however, is when I shock my cat. Most of the time it happens when I'm petting her. The reason why is that when I pet her, I am picking up electrons from her. This gives her a net positive charge and myself a net negative charge. I don't know the magnitude of the charges but we would have equal and opposite charges, assuming I am not grounded and my body contains the electrons, the same with her. When I go to pet her again, our net charges come into contact, and the shock comes from the electrons "jumping" back to her fur and leaving my body. The same sort of thing can happen when you are wearing fuzzy socks or slippers. When you walk, you scrape electrons off of the fabric, and when you go to touch someone, the excess electrons jump onto them in the form of the shock. Likely, part of the reason why you seem to shock more people during the winter is that you wear warmer shoes or socks during the winter, and these items act as better insulators, preventing the net charge on your body from leaving to the Earth.
14. ## Time Travel

That's super interesting. Do you think the human body could go at these high speeds? Would they have to be in some sort of machine or could it be done with some sort of suit?
15. ## Firewatch

For my birthday, I received the video game called Firewatch. You play as a man who went through some rough points in his life, and so you take a job as a forest fire watchman, and you do a little bit more for your boss, Delilah. As you explore your area of the woods, you climb up and down several rock walls using only a rope, and the ropes have been sitting out in the forest for at least three years. I have only seen the character once, and he appears to be about 250 pounds, or roughly 113 kg. I was wondering what the tension would be in the rope as you climb up at a constant speed. This is a fairly easy calculation, where tension would be exactly equal to mass times the force of gravity which is about 1107 N of tension in the rope. This seems slightly unreasonable that the ropes would not snap, especially with consistent use, as they have been weathered by the elements. This photo is a screenshot from the game of how you climb the rock walls .
16. ## Backpacks

I carry all of my school supplies around in my backpack at all times, and it gets pretty heavy at times. I have a binder for all 4 APs, 2 folders, 3 various notebooks, and other odds and ends to get me through the school day. After some light research, I found the average binder weighs 3 pounds, and since my notebooks have the same amount of paper, I'll assume they'll have the same mass. 3 pounds is 1.36 kilograms, and since the other odds and ends probably are around 5 pounds, I converted it to 2.27 kg. This adds up to 11.79 kilograms, which is 115.54 N. This means my back is producing this large of a force to hold my backpack up at a constant height. The straps also have to exert a large force, so make sure you have strong straps on your backpack!
17. ## The Physics of Hydroplaning

While it's dangerous, it's cool that water can affect a heavy car so much, all because of friction!
18. ## WoP #6: Floating Islands

Magnets are a cool force, I'm excited to do more with them this year!
19. ## WoP #8: Tightropes

I always though they were carrying the stick just to carry something heavy, but now I know it's for balance!
20. ## How to pop a tire on a curb

Wow, I knew you didn't want to pop a tire, but I didn't know it could get that bad. If a car going really fast hit the curb, what would happen?
21. ## Chewing French Fries

I am ridiculously addicted to french fries. I don't have a specific favorite place or type of fry that is the best, literally any fried rectangular potato will do for me. I ate some french fries today, and figured why not address the physics behind me chewing my fries. You produce a different amount of force with your molars than your incisors. Men produce about 150 pounds of force with their molars and 83 with their incisors. Females can produce 108 pounds of force with their molars and 57 with their incisors. I happen to be a female, and I chew fries with my molars, so I am going to use 108 pounds of force, or 480.41 newtons. That's alot of force for a french fry! 480 N is about how much force it would take to lift a 50 pound weight at a constant velocity. I would struggle to do that, but I can produce that much force with my jaw with little effort. This wasn't a very in depth look at french fry physics, but this was an incredible thing to learn in my opinion.
22. ## Potential Energy, Kinetic Energy and Cats

If you haven't noticed, I really love my kitten. I am proud to call myself a crazy cat lady in training, but lets not go to far into me, we're here for physics! And I already wrote an all about me. Kittens jump around and run alot. I'm going to track my cats movement for 7 minutes (I like the number 7 so that's why I picked that) and talk about the general physics in her energy. 12:48 - Mia is standing on the ground at first. She then jumps onto my bed, increasing her potential energy. She then further climbs up the back of my shirt, and further increases her potential energy. 12:49 - Mia returns to the bed, decreasing her potential energy from my back. She tries to get into my food. Then she runs around the bed, at a velocity of probably 2-3 m/s, meaning she has some kinetic energy while she runs. 12:50 - Mia takes a trip to the litter. I won't go into further detail. 12:51 - Since Mia is back on the floor, her potential energy is back to where it was at the beginning. She's done a lot, so she gets a quick drink. 12:52 - Mia is again running, but this time on the floor, so she has less overall energy than when she was running around on the bed. 12:53 - Mia needed food. Being a physics subject is hard work, I guess. 12:54 - Mia jumps up onto the window sill, meaning she has increased her potential energy yet again. However, the window sill is lower than my bed, so she has not done as much work as when she jumped onto the bed. 12:55 - Mia runs along the window sill, giving her kinetic energy, and jumps onto the bed from there, increasing her potential energy, and then I pick her up, so she no longer has any kinetic energy, but her potential energy is much higher. I'd like to thank Mia for being such a cooperative test subject and thank you all for reading.
23. ## Cereal

That's so interesting that there's a Cheerio effect. Who knew their were physics in a bowl of cereal!
24. ## Lifting a Cat

As you would know if you have a kitten, they only get worse as they age. This is intensely true for my kitten, Mia. Not only does she constantly escape her room, but she has figured out that my computer screen is touch screen, and wreaks havoc on whatever I am doing on the internet by touching it. I often have to pick her up to try to prevent her from destroying something. She only weighs two pounds, even though she is 13-14 weeks old. I don't have to do much work because of her size, but there is still some being done. 2 pounds equals about .91 kilograms when converted. T-mg = ma would be the equation used to see how much tension is needed to lift her, however there is a flaw in using this equation, which I will discuss later. When I plug in the values, assuming I'm lifting her at a constant speed, the tension would need to be 19.6 newtons in my arm or 9.8 in each of my arms. (Back to the kittens being bad, as I wrote this exact sentence she climbed into my McDonalds bag and started licking my french fries. Kittens are like babies but they move faster and can't really be contained.) But its unlikely I lift her at a constant speed, so lets say I lift her at an acceleration of 1.7 m/s2, just to change it up a bit. Then, when plugging the values in, the tension in one arm would have to be 23 N or 11.5 N in each arm. Back to the problem with this equation. It assumes that the mass of the string (or arm in this case) is negligible, which obviously isn't true since my arms do have mass. This means that my values are off, but this is a high school blog so lets just forget about it for now and pretend my arms don't have mass. Alright, now that that's taken care of, have a nice day!
25. ## My Glasses

Yeah, that's a good point. I would imagine that the force on the glasses from your nose and the muscles there would do a decent amount of work to combat the force of gravity. Thanks!
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