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63 questions in the Category: mechanics.

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1: If an airplane cabin is pressurized, and the atmosphere is thinner as a plane increases its altitude, why doesn't the airplane explode?
2: How can I work out the following:- If a car is stationary and then accelerates to 20m.p.h., what distance will it cover in 1 second, 2 seconds etc. whilst it is still accelerating? The car has a 0-60 mph time of 12 seconds. Will be great if you can help. Thanks. (I would have asked the U.K. science line, but they have run out of funds!)
3: I am afraid of flying. How is it so safe when there are so many working parts. I always believe that the more complicated a machine is, the more likely it is to fail. Can you explain why airplanes don't crash more regularly.
4: Can you explain what changing the gear ratio on your car will do? My sister's boyfriend just ordered new gears and he says that it is going to be a lot faster. How does it make it faster?

I was also wondering what a ground cable does. Everything has one but I've never known what it was really for.

5: Is it possible to use the silk material to replace the steel of reinforcement concrete?
6:

Hi! Thanks for answering my questions.

Lets say two weights are on a board, and their weight is balanced by a log, under the board at the center between the weights. Naturally, if one side of the board is unbalanced it will slowly fall to the ground, making the other weight rise up higher into the air, what are some ways that someone could do that same experiment "wirelessly", in other words, without the board but simply having that energy exchange between the weights be "wireless"?


7:

Hello,
I have a very bright 8th grade student who asked me something I can't answer.

If one were to put some sort of mechanism underneath a big rock that converted the pressure of the rock against the earth into electricity, then how is that not some sort of perpetual energy source? The gravitational potential energy is not changing if the rock is not moving; yet the pressure it exerts must be a kind of energy that can be theoretically converted into electricity, no? The gravitational energy does not "wear out" in this situation... so isn't that a perpetual energy source?

I'm just not sure how to answer his question. He and I both think we understand the basic concepts of gravitational potential energy and kinetic energy. Any guidance you can give us on answering his question would be most appreciated. thank you!


8: I am a Mechanical Engineering student and I want to know simulation process of robots. Could you help me with knowledge about the hardware connections?
9: Hi! I'm still having some trouble with my torque problem. My cone-like object that I described before is rotating on its central axis at a constant speed. How do I calculate the torque and work for this situation. Also, does the mass and height matter, before, you didnt seem to use that in your formulas? Thanks for your help.
10: What is the mechanical advantage of a 6-m long ramp that extends from a ground-level sidewalk to a 2-m high porch?
11: Hi! I hope you are having a happy new year!
How can I calculate how much force (in newtons) a 1/2 in and 1 in thick steel (preferably stainless steel) can take?
Thanks for your help!

12: Hi! I have a question involving some mechanical background. I was wondering where I could get a sort of "circular railing" mechanism. To go into more detail, there would be a rotating cylinder inside of a stationary outer circular part, with some sort of railing mechanism that would allow the cylinder to rotate inside of the circular part. The dimension would be decently large, the rotating cylinder would probably have a diameter of about 12-15 inches. Any info on some sort of "circular railing" mechanisms would be helpful, even something I could make myself. Thanks for your help.
13: How could you know when a Tsunami is coming, how could you detect it when it could be days away or maybe hours?
14: What geometrical shapes create structures that are both strong and light?
15: Hi! Hope you guys are having a great day! I have a question involving a recent experiment that I performed: What I wanted to do was to see if I could contain water using capillary forces, etc. in a "hollow, rectangular tube" (imagine a regular straw, but then making it into a square- shaped straw, and then elongating two of the sides of that square that are parrallel to each other to create a rectangular-shaped "straw") Anyway, I wasnt able to make the shape perfect due to the materials that I was using to create the shape. But it did seem to work fairly well, althought water did begin to slowly fall out of the tube when it was in the vertical position due to some air bubbles that I thought might of formed when I was taking the entire tube out of the water. The dimensions of the rectangular part of the tube were 0.5cm by about 1in or so, so I dont think the tube was big enought to prevent the capillary forces from keeping the water in. Do you guys have any idea why the water might be dripping out of the tube? Would you guys suggest making the tube more water/air tight or making a perfect recangular shape to prevent trapping air bubbles? Or maybe making it smaller? Any info will help. Thank you guys so much!
16: Is it possible to propel a car's Internal Combustion Engine using nothing but compressed air?
17: Hi! Do you guys know where I could get some "frictionless" or nearly "frictionless" bearings? I need some for an experiment where I have to essentially eliminate friction. Thank you for your help.
18: Two other friends and I are conducting a science fair project in which the question is: How does different footwear, or lack thereof, affect running ergonomics? There are many tests we can conduct with our own equipment, but a great addition to the project would be access to forceplates and any other instruments to measure weight distribution and or the stresses and forces incurred on the body while in the process of running. If no one working at the university has the means to test these things a nudge in the right direction would be much appreciated!
19: How are the electrons attached to the atom? Is there a way in which they are arranged around the nucleus?
20: Why does different soils effect footprints/tracks? Why does mud shows good footprints/tracks compared to other soils? How does water change the footprint/track? How did you become a scientist in this criteria? How long did it take you to become a scientist?
21: How do you think the barrel length affects the accuracy and range of a projectile? Why do you think this happens? What is your field and how long have you been working in it? If you were to build a air cannon would you build a long medium or short barrel? What do you think would be the beast projectile for a air cannon?
22: Which type of waves do we have when there is an earthquake?
23: A teacher at this school did a science experiment where he had two balls of different masses go down an incline which was raised about 20cm above the table. The balls were released from the same point on the incline and he assumes they accelerated at the same rate and so when they left the incline they were going at the same speed (I'm not sure this is true). In any case, the ball with the larger mass hit the table at a farther distance than the ball with the smaller mass. Could this be true if they were going at the same speed when they left the incline? It seems to me that they should hit at the same place. I don't think the friction of the air would cause enough resistance to cause any difference. The larger ball would have more momentum but this shouldn't affect the rate at which a ball falls. Am I missing something or what accounts for the different distances the balls go through the air?
24: How do airplanes fly? What helps airplanes fly? How do airplanes manage to get in the air? What makes an airplane stay in the air? I got a paper out of the computer that gave me some Information about different pressure on the wings, but not enough to make it clear.
25: Im interested in airplanes. I want to know how they make the engine balance to the wings because the engine seems heavier than the wings and still keep the airplane on the air?
26: Do trains have gears? How fast can an old steam train go? Who invented the first train? What train is the fastest today? Why do trains have a side rod?
27: Some questions about telephones:1. Do some telephones have capacitors and other telephones don't? 2. Do all phones work the same? 3. Why do you have to have a particular kind of portable phone to use in a car? 4. Can you call from an ordinary phone into space?
28: How does video tape make contact with the VCR?
29: What kind of fuel does an F-22 Raptor and a F-16 use? (fighter jets) What are the best fighter jet and bomber from your point of view ?
30: Why do we have toes?
31: What causes spontaneous combustion?Extra question from those X-Files fans: Can humans spontaneously combust?
32: I am currently participating in a project where I have to design a space settlement. I would like some data on the materials and the processes being developed/studied here. If you have any such information, could you help me?
33: When a skateboard rolls to a stop, is most of its Kinetic Energy (KE) lost as heat in the ground, the wheels' surface, or in the ball bearings...of the wheel. Also, if two skateboards are in motion (A and B), and the wheels, ball bearings,.. of B have a higher heat capacity than A, would this mean that skateboard B would roll longer?
34: We are discussing Newtons and I was wondering how you measure Newtons. How do you know when you are pushing 40 N agianst someone. What makes a Newton a Newton?
35: How do we get the satellites to other planets like Jupiter so fast if it takes a regular rocket 5 years to get there?
36: How do CDs work?
37: Are scientists measuring the stress under the Ocean plates closed to the California coast? How do they do that?
38: What type of sound waves does an accordion produce?
39: Does the sun rotate?
40: What is the main difference between a Newton meter and a spring balance?
41: What part of a motor transforms electricity into movement? It is not like you sap an RC car and it starts moving.
42: Do basketballs that are fully inflated bounce better than flatter ones?
43: What would happen if there were an explosion and an implosion at the same time?
44: Because paper airplanes are small, would they fly faster? If not, why?
45: How do sound waves travel?
46: If paper airplanes are small will they fly faster?
47: How much harder an aluminum bat would hit a ball compared to a wooden bat?
48: How fast the stream train travels?
49: How do particles in a fluid exert pressure on a container?
50: What does each dark, long line on the spring scale represent? And what do the lighter smaller lines on a spring scale represent?
51: I like inventing mechanical things, what kind of Scientist can I be?
52: Why does the mass of a particle changes when its speed changes?
53: How does a pendulum clock work?
54: When I raced a derby car, I was told that adding a fender for the front side of the rolling wheels would deflect the oncoming air (from the car's point of view) allowing the car to go faster. However, when I recently saw a formula for drag, I noticed a "speed of the media" component. Thinking through the speed of the wheel from the body point of view, the forward surface of the wheel above the axle is rotating into the oncoming air at faster than the forward linear motion of the car body, and the forward surface of the wheel below the axle is traveling forward at a slower rate than the body of the car (the tread touches the track). This leads me to ask: Are fenders only aerodynamically effective for shielding the forward surface of the upper half of the rolling wheel, and counterproductive for shielding the front surface of the lower half of the rolling wheel?
55: If you were to cut up a piece of fruit, which has cells in it, would you be cutting apart molecules then too? How about atoms? And if you cut apart the atoms that make up the organelles of a cell, why don't we hear as big of an explosion as we do when we are splitting atoms up in bombs?
56: What are the important facts about plastics?
57: I recently read here that high performance military jets use kerosene for fuel due to it's higher energy density. If these planes can use kerosene, why do 'normal' jet engines use high octane jet fuel? Am I missing something? Thanks!
58: If we throw a ball vertically downwards on the ground, is the force of that ball absorbed by the ground?
59: Do all snakes hibernate?
What Skeletal/Muscular systems contribute to their movement?
How do snake species inject venom and do they all inject venom the same way?
Thank you for taking the time out of your busy day to answer my questions. I would personally like to thank you for all your hard work that you do to preserve wildlife through out the world.

60: Why will a person/animal (i.e. dog) continue to travel in a straight line while jumping (assuming initial trajectory to be a straight line) despite twisting motion? (i.e. attempt to twist left/right when viewed from above)? Intuitively I know it is not possible to alter the trajectory without input of an external force, I just don't know how to really explain it.
61: How do I Program Robots?
62: Which metal is not only dense and heavy like osmium, but is also most resilient? In other words, does osmium's density make it the metal with the strongest atom bonds, or will it crack if struck hard enough, like tungsten for instance?If weight, density, AND impact resilience are the criterion, what metal is strongest?
63: According to the third Newton's law: every action has an equal and opposite reaction. Then, both action should get cancelled and the body should remain constant. My question is, why does a bullet move from a gun according to this law?
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