So this winter break was really fun and thankfully pretty restful…I wish it didn’t have to end so soon :/ But now on to the physics part. During our very cold soccer trip to San Francisco, you couldn’t help but being surrounded by the stuff. Even in our transportation—from our airplane ride into SFO, our van rides to the field, and BART ride into the city, we experienced displacement and acceleration among other things. Our total displacement for our trip for example was zero because we flew a bunch of miles to San Francisco, but flew about the same mileage back to Honolulu (in the opposite direction). While in our vans, we exerted a weight on the road which exerted a normal force back, allowing us to drive on the road. On the BART, we went through both positive and negative acceleration as we travelled in opposite to and from the city (Union Square). And even though we didn’t ride the cable cars this time, we watched them run up and down Powell Street as we went in and out of the stores. These cable cars run on a system of underground steel cables and pulleys, maintaining a constant velocity and tension. The actual soccer portion of our trip also embodied physics. When we struck the ball to make a pass or take a shot, we most of the time hit the ball off center, exerting a torque on the ball and therefore causing the ball to spin. And even though most of us can’t bend it like Beckham (yea that’s us, haha)…we could curve the ball enough for the most part to avoid a defender or play a good cross into the box. So here's us in our van, on the BART, with David Beckham ;) and making a pitstop on the way back to the hotel next to a really pretty tree. Wow that's a lot...I guess I'm feeling picture happy tonight
Back at home physics was present as well. Last night some of my friends and I went to Hawaiian Brian’s and played pool..and I didn’t lose! Well as the cue ball struck another ball, I witnessed an elastic collision and saw energy (almost completely) being conserved…just like in our homework problems. The initially stationary cue ball would move thanks to an outside force (you and your pool stick) then would transfer its kinetic energy to the ball you are aiming for. This exchange along with the help of the friction between the ball and the pool table causes the cue ball to stop and hopefully (if you’re good) the other ball to roll into a pocket.
Merry Christmas and Happy Holidays!
This past weekend while at my grandparents’ house, my cousins brought their airsoft guns. So we went to backyard to play with them and shoot some cans and water ballons while we waited for lunch to be ready. Airsoft has a lot to do with physics. The guns which we used were electric and were powered by rechargeable batteries. My uncle said that the batteries power an electric motor that turns a gear box or something which compresses a spring. The tension from the spring is then released, sending the plastic BBs through a chamber and out of the barrel. The tension created in the spring must be pretty immense because those BBs fly right out of those guns! With such small masses, it makes sense that they move so fast. However, a smaller mass leaves the BBs susceptible to wind and stuff which can lower accuracy. So, different masses of BBs are used. But if you think about it, the pellets can’t be that heavy, or else they wouldn’t be able to move quickly or hit far targets, so their amount of KE transferred can’t be that big (E=1/2mv2). This means that BBs aren’t super damaging, when compared to larger paintballs for example. I learned this firsthand when my cousin shot me in the leg. Because of the small mass of the pellet and long distance between me and him and his gun, the shot hurt, but not that much. This makes sense because since the pellets we were using were of a small mass, they had small inertias. And although they were shot at higher velocities than other heavier pellets would be, they also lost speed quickly; therefore minimizing the hurt I felt when the BB finally reached me. The flight and flight path of the pellets also are physics related. When we shot the BBs this weekend, because we were aiming for cans and other things close by, their paths appeared perfectly horizontal. But when shooting the gun at a slightly upward angle the other weekend, I could see the parabolic flight of the pellet. My neighbors own Toys n Joys and my uncle likes to play with the airsoft guns. So the other weekend he brought home an airsoft gun that had this tracking thing so the pellets glowed in the dark! It was a perfectly clear and dark night so we all stopped our football game and told our uncle to get the gun. Standing in his driveway, my uncle aimed the gun kind of upwards and we could see its path clearly...it was parabolic :-) The way the BBs fly is physics too and is at the hand of Bernoulli’s principle—the same principle through which airplanes get lift. Airsoft—more fun thanks to physics.
