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prettybird

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  1. prettybird

    Falling Paper

    By prettybird,

    One thing I do on a daily basis is drop things. For example, pieces of paper or folders. When these things fall, they have the force of mg down, and the force of air resistance up. The paper will reach a terminal velocity and continue to fall at this velocity until it hits the ground. The force that the paper exerts on the floor is equal to the force the floor exerts on the paper. The coefficient of friction between the tile floor and the paper is likely small because the tile is smooth and the paper is also relatively smooth. This means that if the paper was acted on by some force, it would move easily across the floor. When I go to pick up the paper, since the paper's inertia is small, it is easy to pick it up. When I pick up the paper, I increase its potential energy (found by mgh) as I increase its height. When I set it back down on the table, the normal force from the table stops it from going through the table and opposes the force of gravity on the paper.
  2. prettybird

    Physics with Mia

    By prettybird,

    I recently got an 8 week old kitten on September 20th and have been spending all my time watching her and keeping her out of trouble (not only has she stepped on my keyboard an uncountable amount of times while I wrote this, she also deleted the whole thing twice). I figured I'd kill two birds with one stone and do some physics with her in mind.
    She often jumps off of my bed, so I figured I'd find her final velocity the instant before she hits the ground. I know her vertical acceleration due to gravity is 9.8 m/s2, and that her initial vertical velocity is zero, as well as her horizontal acceleration. I filmed her running off the edge of the bed and determined she covered around 13 cm (.13 m) before she left the bed, and she did this in around .4 seconds. I also know she falls about 42 cm (.42 m) when leaving the bed.
    I determined her initial horizontal velocity to be .325 m/s by using the equation v = x/t. I then found the final vertical velocity using vf2 = vo2 + 2ax, which gave me 2.87 m/s. I then used pythagorean theorem to attain the true final velocity, which came out to be 2.89 m/s. 
    I decided to convert this into some other popular units, just because I was curious, and came out with 9.48 ft/s and 4.98e-7 mph. 
    And here's a picture of her while I'm writing this blog post.

  3. prettybird

    Shoot Your Grade Lab

    By prettybird,

    Our class was given the task to collaborate on a lab to find the distance a ball would go when fired and place a target where we believed it would land. The class was allowed to fire the ball once, then the ball would be moved and the angle would change. Together, we took measurements of the first setup, and started doing calculations. We worked in small groups and compared answers, coming to a conclusion that the initial velocity of the ball was around 4.65 m/s. This allowed us to start to calculate the distance the ball would travel at the new height and angle.
    However, the class was running out of time and out of desperation, the book was placed at a randomly predicted location and the ball was fired. It missed the target slightly. We were told to redo the calculations and find out what went wrong. The problem was that the target was placed without finishing the calculations, and therefore there was little chance for us to be right.
    The initial velocity was 4.65 m/s, and the ball was being fired at -4 degrees, meaning that the ball started with a horizontal velocity of 4.64 m/s and a vertical velocity of .32 m/s. The accelerations for the two directions were 0 m/s2 (horizontal) and 9.8 m/s2 (vertical). The vertical displacement would be 1.035 m once the ball was fired.
    The equation y = vot + (1/2)at2 allowed me to determine the time the ball would take when traveling to the target. I used the quadratic formula, which gave me .43 s and -.496 s. The negative time was discarded as time cannot be negative. I then used the same equation (x = vot + (1/2)at2) to find the distance the ball would travel, which was 1.995 m.
  4. prettybird
    Overall, I have been enjoying the first few days of physics class and reviewing the content we learned last year. It was generally pretty easy. However, let me talk about scientific notation. I thought I was good at it before this year, but I guess not. I read the first chapter of the textbook and watched the first lecture and figured I was well prepared to start the intro WebAssign. For some reason, the scientific notation problems gave me the most trouble. I re-read the chapter, and figured I'd give it another go. Again, no luck. I followed all the rules in the textbook and I still could not get these problems to work. I finally decided to type it all into my calculator exactly as the problem stated just to see how these ended up and still I could not get the right answer for the last one. Somehow, I cleared the entry from my calculator and when I finally realized I had forgotten a negative sign somewhere I had to type it all in again, which took another 10 minutes.
    Overall, Physics - 1, Me - 0.
  5. prettybird
    Makeup is one of my biggest interests, however I wake up late a lot of the time and don't have time to put it on. It's fun to be creative and almost create art on your face, and to show it off for a day. 
    The big physics principle behind makeup is trying to combat the force of gravity and using friction to help the makeup apply. 
    All the makeup on your face is applied with some amount of friction helping you out. Whether you're applying lipstick from the tube or using a brush to put on eyeshadow, you're counting on friction to put that stuff on your face.
    You also count on that force of friction to keep your makeup on your face throughout the day. If there was no friction, the makeup would fall right off your face.
    (Below are some selected favorites from my collection which all demonstrate this physics principle. Also, my cat Mia is a diva and had to be in the photo.)

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