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Question about Weight..
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by i_want_to_flirt_with_drunk_sango
on 2006-07-10 12:47:22 (edited 2006-07-10 12:48:08)
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In my "Riddle" thread a riddle was presented about an 800 pound gorilla crossing a bridge with three 100 pound balls of gold, and attempting to cross the bridge without exceeding a 1000 pound weight limit on the bridge (while carrying all three balls of course) . Now, the answer is too juggle the balls and cross the bridge that way, and that is the logical answer, but what about when you examine this from a scientific point of view out of curiosity? QUESTION: If an 800 pound gorilla crossed the bridge juggling the 3 balls, couldn't the force required for him to juggle the heavy balls actually come out to over 1000 pounds of pressure on the bridge, and therefore exceed the weight limit? This may take someone with physics and math skills. And I came up with this because I remember standing on a scale and if you pushed force on the scale with your feet the weight would increase, even though it was not your actual weight. After all, isn't weight as we think it just the gravity on your mass, and also coupled wiht your own force? I know it's not the most seriuos qeustion, but it is an interesting way for me to learn about weight and force... |
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Re: Question about Weight..
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by
on 2006-07-10 19:33:51 (edited 2006-07-10 19:53:31)
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Bridges are often rated by how much force they can handle at one time before breaking. Weight is a measure of force. You will notice that when can bounce up and down on a scale, the reading goes wild. This is because you are applying a non-uniform force to the scale. When you walk on a bridge, the same thing happens, you bounce as you walk, so a bridge that can hold up to 1,000 pounds before breaking may still be broken by a stomping gorilla. When you catch a ball with your hands, you get a lot more force than the weight of the ball. This is because you have to decelerate the ball quickly by pushing upwards with your hands. A gorilla throwing a 100-pound ball in the air would get well over 1,000 pounds of instantanious force applied upon catching said ball. The gorilla will fall to his/her circus-like death. A better idea would be to throw the balls across the bridge, or roll them across. 
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Re: Question about Weight..
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by i_want_to_flirt_with_drunk_sango
on 2006-07-10 20:17:48 (edited 2006-07-10 20:19:09)
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About the riddle, yeah it would be easier to roll the balls or throw them, but the riddle forbid those methods; and as I suspected the gorilla would exert enough force to exceed the 1000 lb. limit! Anyhow, I found some interesting things and relevant to the subject while researching this on Wikipedia, particularly about "microgravity", very interesting and you can find it there under weight for more info, and I wanted to share some of it with anyone who reads this thread: "The weight force that we actually sense is not the downward force of gravity, but the normal (upward) force exerted by the surface we stand on, which opposes gravity and prevents us falling to the center of the Earth. This normal force, called the apparent weight, is the one that is measured by a weighing scale. For a body supported in a stationary position, the normal force exactly balances the earth's gravitational force, and so apparent weight has the same magnitude as actual weight. (Technically, things are slightly more complicated. For example, due to the earth's rotation objects are subject to a small centrifugal force, varying with latitude, which partially offsets gravity. The normal force therefore balances a force slightly less than the true force of gravity.) If there is no contact with any surface to provide such an opposing force then there is no sensation of weight (no apparent weight). This happens in free-fall, as experienced by sky-divers and astronauts in orbit who feel "weightless" even though their bodies are still subject to the force of gravity. The experience of having no apparent weight is also known as microgravity. A degree of reduction of apparent weight occurs, for example, in elevators. In an elevator, a spring scale will register a decrease in a person's (apparent) weight as the elevator starts to accelerate downwards. This is because the opposing force of the elevator's floor decreases as it accelerates away underneath one's feet." Unfortunatley, at Wikipedia I couldn't find info on the way or an equation to measure the force needed to juggle the balls into the air so that I could add that weight to the gorilla and figure out exactly how much weight he exerts on the bridge, before he breaks it! It's problaby there but I'm just not seeing it yet; I need to review more since it's all new to me. It's just for fun though, because I've recently become interested in Physics as another side interest thanks to Gendou and Wikipedia; also I'd like to take classes (for credit not career) on Physics next year and have some knowledge and experience to work off of prior. |
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Re: Question about Weight..
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by humblemonkey
on 2006-07-14 13:33:16
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Taking physics is something everyone should do. Lots of things make great sense after that. :) Elementary physics would help you solve this problem. But in order to do that you have to have some more constants to make things easier, like, how high would the gorilla juggle the balls? Would the height be the same for every ball, or would it vary? Now I'm kinda interested in solving it... but why golden balls? lol |
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Re: Question about Weight..
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I don't know if this happens everywhere, but I get the feeling college physics is far more interesting than high-school physics. Or maybe I had bad teachers in high school. However, I did once solve a similar problem in high school once: it involved something falling onto a scale, and you had to calculate the max weight the scale would indicate. It's like you guys said: the one thing that's really needed here is the amount of deceleration done (since "weight" simply means the normal force being applied). On the gorilla question, I believe you'd need the height the balls are juggled (to know the speed they reach the gorilla's hand) and the time it takes to the gorilla to decelerate the balls (so you get the force he's making to stop them). You would also need to know about how he throws the balls, but I'm getting way too nerdy here XD Now, generically speaking... If we had the values in a way that the weight of the gorila 2 balls would be UNDER the max weight, but the gorilla 3 balls would be above, would juggling the balls ever work? Let's say the gorilla had 750 pounds... Is it possible then? Now I'm puzzled...
"From East Middle School, Suzumiya Haruhi.
I'm have no interest in ordinary humans. If there are any aliens, time travelers, sliders or espers here, then come join me."
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