|
Reasoning questions in physics
| |
| scienceclub | Date: Monday, 15-Dec-2014, 11:25 AM | Message # 1 |
|
Lieutenant
Group: Administrators
Messages: 72
Status: Offline
| 1. The four compass directions North, East, South, West are derived from old foreign words. Can you match up the original meanings with the compass directions:
A – Indo-european wes = sun goes ‘down’; B - Italian nerto = ‘to the left’ as one faces the sun;
C – German suntha = region in which the ‘sun’ appears in the northern hemisphere;
D – Indo-european aus = sun ‘rises’.
2. Consider the Earth to have a circumference of 40 000 km and a ribbon to be put tightly around it. If you cut the ribbon and inserted a 30 cm piece, how far will the ribbon be from the Earth if it was evenly spaced?
3. A car travels from A to B at an average speed of 100 km/h and returns at 60 km/h. What is the average speed for the journey?
4. A man goes from A to B at 30 km/h. How fast must he return to average 60 km/h for the whole trip?
5. If you put a row of coins on a 1 metre ruler which has one end on the ground and let the other end fall – which coins will stay on the ruler and which ones will be left behind?
|
| |
| |
| scienceclub | Date: Monday, 05-Jan-2015, 12:51 PM | Message # 2 |
|
Lieutenant
Group: Administrators
Messages: 72
Status: Offline
| The path to enlightenment lies behind one of two doors. In front of each door stands a guard who knows which door leads to enlightenment, but one of the guards always lies and the other one always tells the truth. In your search for enlightenment, you are allowed to ask one guard only one question that can be answered "yes" or "no", but unfortunately, you do not know which guard is the liar. You will be banished to the dungeon of logical illiteracy if you fail in your quest. What question should you ask to find the path to enlightenment?
|
| |
| |
| scienceclub | Date: Monday, 05-Jan-2015, 12:52 PM | Message # 3 |
|
Lieutenant
Group: Administrators
Messages: 72
Status: Offline
| Answer for the above logical puzzle..
If you ask a guard directly "Are you guarding the path to enlightenment?", and the answer is "no", he could be guarding the path to enlightenment and be lying about it, or he could be telling the truth and the path to enlightenment is behind the other door.
The question that you ask has to involve both guards at the same time:
"Would the other guard say that you are guarding the path to enlightenment?"When we ask a guard this question, there are 4 cases:
The liar is guarding the path to enlightenment. He answers "no" because the truthful guard would say "yes".
The liar is not guarding the path to enlightenment: He answers "yes" because the truthful guard would say "no".
The truth teller is guarding the path to enlightenment. He answers "no" because the other guard (liar) would say "no".
The truth teller is not guarding the path to enlightenment. He answers "yes" because the other guard (liar) would say "yes".
So, if a guard answers "no", he is guarding the path to enlightenment. If he answers "yes", the path to enlightenment is the other door. Notice that even though we have learned which is the path to enlightenment, we still don't know which guard is the liar. To find out who is the liar we would have to ask a question like: "Would the other guard say that you always tell the truth?" A reply of "no" means you are talking to the truth teller, a reply of "yes" means you are talking to the liar.
|
| |
| |
| scienceclub | Date: Monday, 05-Jan-2015, 12:56 PM | Message # 4 |
|
Lieutenant
Group: Administrators
Messages: 72
Status: Offline
| A valuable painting was stolen from the Liars' Club, but the police are having a hard time identifying the culprit because every statement made by a member of the Liars' Club is false. Only four members visited the club on the day that the painting was stolen. This is what they told the police:- Ann: None of us took the painting. The painting was here when I left.
- Bob: I arrived second. The painting was already gone.
- Chuck: I was the third to arrive. The painting was here when I arrived.
- Tom: Whoever stole the painting arrived before me. The painting was already gone.
Who of these four liars stole the painting?
|
| |
| |
| scienceclub | Date: Wednesday, 04-Feb-2015, 11:23 AM | Message # 5 |
|
Lieutenant
Group: Administrators
Messages: 72
Status: Offline
| Big Questions in Heliophysics:
- What causes the sun to vary?
- We live in the extended atmosphere of a magnetic variable star that drives our solar system and sustains life on Earth. Our Sun varies in every way we can observe it. The Sun gives off light in the infrared, visible, ultraviolet, and at x-ray energies, and it gives off magnetic field, bulk plasma (the solar wind) and energetic particles moving up to nearly the speed of light, and all of these emissions vary.
- How do the Earth and Heliosphere respond?
- Our planet is immersed in this seemingly invisible yet exotic and inherently dangerous environment. Above the protective cocoon of Earth’s lower atmosphere is a plasma soup composed of electrified and magnetized matter entwined with penetrating radiation and energetic particles
- What are the impacts on humanity?
- Modern society depends heavily on a variety of technologies that are susceptible to the extremes of space weather — severe disturbances of the upper atmosphere and of the near-Earth space environment that are driven by the magnetic activity of the Sun. Strong electrical currents driven in the Earth’s surface during auroral events can disrupt and damage modern electric power grids and may contribute to the corrosion of oil and gas pipelines.
|
| |
| |
| scienceclub | Date: Tuesday, 05-Apr-2016, 5:29 PM | Message # 6 |
|
Lieutenant
Group: Administrators
Messages: 72
Status: Offline
|
1.
Radiocarbon is produced in the atmosphere as a result of
A. collision between fast neutrons and nitrogen nuclei present in the atmosphere B. action of ultraviolet light from the sun on atmospheric oxygen C. action of solar radiations particularly cosmic rays on carbon dioxide present in the atmosphere D. lightning discharge in atmosphere
|
| |
| |
| scienceclub | Date: Friday, 08-Jul-2016, 11:25 AM | Message # 7 |
|
Lieutenant
Group: Administrators
Messages: 72
Status: Offline
| Big Questions of Astrophysics from NASA
1. How does the universe work?
Understanding the universe's birth and its ultimate fate are essential first steps to unveil the mechanisms of how it works. This, in turn, requires knowledge of its history, which started with the Big Bang.
Previous NASA investigations with the Cosmic Microwave Background Explorer (COBE) and the Wilkinson Microwave Anisotropy Probe (WMAP) have measured the radiation from the universe when it was only 300,000 years old, confirming theoretical models of its early evolution. With its improved sensitivity and resolution, ESA's Planck observatory probed the long wavelength sky to new depths during its 2-year survey, providing stringent new constraints on the physics of the first few moments of the universe. Moreover, the possible detection and investigation of the so-called B-mode polarization pattern on the Cosmic Microwave Background (CMB) impressed by gravitational waves during those initial instants will provide clues for how the large-scale structures we observe today came to be.
Observations with the Hubble Space Telescope and other observatories showed that the universe is expanding at an ever-increasing rate, implying that some day - in the very distant future - anyone looking at the night sky would see only our Galaxy and its stars. The billions of other galaxies will have receded beyond detection by these future observers. The origin of the force that is pushing the universe apart is a mystery, and astronomers refer to it simply as "dark energy". This new, unknown component, which comprises ~68% of the matter-energy content of the universe, will determine the ultimate fate of all. Determining the nature of dark energy, its possible history over cosmic time, is perhaps the most important quest of astronomy for the next decade and lies at the intersection of cosmology, astrophysics, and fundamental physics.
Knowing how the laws of physics behave at the extremes of space and time, near a black hole or a neutron star, is also an important piece of the puzzle we must obtain if we are to understand how the universe works. Current observatories operating at X-ray and gamma-ray energies, such as the Chandra X-ray Observatory, NuSTAR, Fermi Gamma-ray Space Telescope, and ESA's XMM-Newton, are producing a wealth of information on the conditions of matter near compact sources, in extreme gravity fields unattainable on Earth.
|
| |
| |
| scienceclub | Date: Friday, 08-Jul-2016, 11:25 AM | Message # 8 |
|
Lieutenant
Group: Administrators
Messages: 72
Status: Offline
| 2. How did we get here?
In order to understand how the universe has changed from its initial simple state following the Big Bang (only cooling elementary particles like protons and electrons) into the magnificent universe we see as we look at the night sky, we must understand how stars, galaxies and planets are formed.
There are many questions associated with the creation and evolution of the major constituents of the cosmos. A basic question astronomers must address is, how did the universe create its first stars and galaxies? Once these entities were created, how did they influence subsequent galaxy, star and planet formation? This is an important question, because these later objects are made of elements that can only have been created by the first generation of stars.
It is still unknown whether the universe created black holes with the first generation of stars or whether these exotic objects were created by the first generation of stars. Because black holes represent the most extreme physical conditions of spacetime and generate some of the most energetic phenomena following the Big Bang, they are the ultimate physical laboratories for testing theories of the universe.
We now know that our universe has a "foamy" structure. The galaxies and clusters of galaxies that make up the visible universe are concentrated in a complex scaffold that surrounds a network of enormous cosmic voids. However, in addition to the "normal" matter that makes up the visible parts of the universe, scientists have discovered that there are vast amounts of unseen matter. This so-called, "dark matter" makes up roughly 27% of the matter-energy content of the universe, while the visible pieces account for only about 5% of the total. Clearly, if we hope to understand the structure of the universe and the processes by which it formed and evolves, we must first understand the distribution of this important but unseen dark matter and the ways in which it interacts with and influences normal matter.
Though astronomers have been studying stars for thousands of years, it is only in the past 35 or so years that they have been able to employ instruments that detect light across the entire electromagnetic spectrum–from radio waves to gamma rays–to peer into the dusty clouds where stars are born in our own Galaxy. If we are to comprehend how the universe makes stars–and planets that orbit them today–we must continue these studies with ever more powerful telescopes.
|
| |
| |
| scienceclub | Date: Friday, 08-Jul-2016, 11:27 AM | Message # 9 |
|
Lieutenant
Group: Administrators
Messages: 72
Status: Offline
| 3. Are we alone?
This question is as old as humankind itself. For millennia, people have turned their eyes to the stars and wondered if there are others like themselves out there. Does life, be it similar to our own or not, exist elsewhere in our Solar System? Our Galaxy? Until 1992, when the first exoplanet was confirmed, it was uncertain whether there were even any planets outside those in our own Solar System. Today we know of over 1700 planets around other stars and thousands of planet candidates. Do any of these planets have conditions that would support life? What conditions favor the formation of terrestrial-class planets in developing planetary systems? NASA can help address these questions by developing missions designed to find and characterize extrasolar planetary systems.
Before we can determine if there are other planetary systems capable of supporting life, we must first find them. NASA Science pursues this goal by supporting a focused suite of ground-based observations through the Kepler mission, a space-based observatory which studied the prevalence (how many there are per star) of extrasolar planets, and through the development of the TESS mission which will use an array of telescopes to perform an all-sky survey to discover transiting exoplanet ranging from Earth-sized to gas giants.
|
| |
| |
| Team-scienceclub | Date: Saturday, 09-Jul-2016, 11:33 AM | Message # 10 |
|
Private
Group: Administrators
Messages: 1
Status: Offline
| Two bulbs of 40W and 60W are connected in series with an AC power supply of 100V. Which bulb will glow brighter and why?
Dave Larsen, 14 years, industrial electrician 58.1k Views · Most Viewed Writer in Electricity with 210+ answers
I think we need to tip our hat to Kirchoff for this one...
I'll try to piece together what I can remember- I think the voltage is a red herring here, because it's an issue of proportion. At any voltage above zero (within the capacity of the bulbs) one will be proportionately brighter. The 40 watt bulb hooked in parallel is normally dimmer because the filament has a higher resistance than that of the 60-watt bulb. But we're dealing with a series circuit here...
- Assuming the bulbs were manufactured to operate at 120 volts; I=P/E, I=60/120, I=0.5 amps for the 60 watt bulb; R=E/I, R=120/0.5, R[60]=240 ohms. The 60 watt bulb has 240 ohms resistance when burning
- I=P/E, I=40/120, I=0.3333 amps; R=E/I, R=120/0.3333, R[40]=360 ohms. The 40 watt bulb has 360 ohms resistance when burning
- Series resistances add directly so 240 ohms + 360 ohms =600 ohms total resistance
- So in your 100 volt application; I=E/R, I=100/600, I=0.1666 amps. Your total circuit current is 0.1666 amps
- All points in a series circuit see the same current so....
- Volt drop at the 40 watt bulb: E=I*R, 0.16666 * 360 = 60 volts of drop
- At the 60 watt bulb; E=I*R, 0.16666 * 240 = 40 volts of drop
The calculated voltage drops add up to the total voltage so Kirchhoff should be happy, and the drop at the 40 watt bulb is bigger.
Sooooo......
- At the 40 watt bulb; P=E[d]*I; P=60*0.1666; P= 10 watts
- At the 60 watt bulb; P= [d]*I; P=40*0.1666; P = 6.6666 watts
More watts burning means brighter light from the 40 watt bulb.
Really? That seems weird. But I also calculated these numbers using the I squared Rformula and got the same result. Am I missing something here?
Sai Teja Mulpuru, Soon to be an Electrical Engineer. Studying @ IIT(BHU) Varanasi4.2k Views
The 40W bulb will glow brighter than the 60W bulb.Any light bulb is given a wattage at the voltage at which it is going to be used(which is usually fixed at 110V or 220V depending on the region).Its wattage depends on the resistance of the filament in the bulb as P=(V^2)/R , hence R for a 40W bulb is 1.5 times that of a 60W bulb.The power output by a light bulb(or in fact any appliance with only resistance) is (I^2)*R. Since both the bulbs are in series, the same current flows through them. But theresistance of the 40W bulb is higher than the 60W watt bulb, Hence the power output by the 40W bulb will be higher than the 60W bulb in this case.Hence the 40W bulb will glow brighter in this case.(This answer assumes that both the bulbs used are rated for same voltage which is almost always true.)Written Mar 14 · View Upvotes
John Gerig, fixed radios when other teens mowed lawns!12.6k Views
Sometimes, in thinking about problems like this, it helps to consider more extreme cases. In the present case, we could for example think about a 10W and a 1000W bulb in series, in which case it would (hopefully) be obvious that, relative to the resistance of the 10W bulb, the 1000W bulb would be a virtual short circuit, and almost all of the applied 100V would appear across the 10W bulb.Written Jul 1, 2015 · View Upvotes · Answer requested by Iftikhar AhmedAdded (09-Jul-2016, 11:33 AM)
---------------------------------------------
Pavankumar Devadurgam, Preparing for engineering services30 Views
If we consider both the bulbs having the same Voltage rating( assuming it to be some 100V) then the corresponding resistances of bulbs will beR1 = 100*100 / 40 = 250 ohmR2 = 100*100 / 60 =166.66 ohmHence resistance of 40W bulb will be greater than 60W bulb.Now going back to the asked scenario,as they both are in series,current flowing through them will be same. Hence power absorbed by bulb1 of 40W is more(since resistance is more) than the power absorbed by the bulb2 of 60W( since resistance is less). Thus first bulb will glow brighter i.e of 40 W.Note : If both the bulbs dont have same voltage rating then above solution is not valid and it needs to be solved differently.Written Fri
Binita Kumari Dash, I'm a B. Tech graduate in EE, and now pursuing M. Tech1.9k Views
The 40W bulb will glow brighter than the 60W bulb.
Since the power ratings of the bulbs are known, we first need to calculate the bulb resistance. Because a bulb is made of wound wire of some resistance which when heated provides light.
Now, we know, power, P= V^2 /R
So, for 40W bulb,
R1 = (100*100) /40 = 250 ohm
For 60W bulb,
R2 = (100*100)/60 = 166.6666 ohm
Now, since these two are connected in series, the current flowing through both of them is same. So, the coil in which more heat is produced will glow brighter.
Now, W = I^2 *R*t
Since, I and t are same for both of them, so who has higher resistance will be brighter.
So, the 40W bulb having a higher resistance of 250 ohm will glow brighter.Written Apr 29 · View Upvotes
Sonika Chandela, ELECTRICAL ENGINEER FROM NIT KKR364 Views
In practical life ,bulbs are connected in paralles i.e same voltage therefore using ,p = v^2/R .since the power is inversly proportional to the resistance ,therfore the 40 W bulb has more resistance than the 60 W bulb .now according to your question ,they are connected in series therefore using p=(I^2)R ,becoz series means they have same current flowing throw them .now since power is directly proportional to the resistance and since the 40W bulb has high resistance than 60 W bulb therefore THE 40 W BULB WILL GLOW MORE BRIGHTER THAN THE 60W BULB.
|
| |
| |
| kayto555666 | Date: Wednesday, 27-Sep-2017, 5:11 AM | Message # 11 |
|
Private
Group: Users
Messages: 3
Status: Offline
| I found a company that can to you herein to help and will write your essay for you. I worked already with them, they had written to me an excellent essay on physics. https://cheapcustompapers.com/
|
| |
| |
|
