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A student measures the time period of 100 oscillations of a simple pendulum four times. The data set is 90s,91s,92s & 95s. If the mimimum division in the measuring clock is 1s, then find the reported mean time ?

Posted by Saurav Kumar (Jun 23, 2017 9:59 p.m.) (Question ID: 6136)

• Let’s  first  find  the mean  value  of time:

{tex}t_{mean}={t_1+t_2+t_3+t_4\over 4}{/tex}

{tex}{90+91+95+92\over 4}= 92 {/tex}

Then,  we can  find  the  absolute error for each  measurement:

{tex}\Delta t_1=|t_{mean}-t_1|= |92-90|=2{/tex}

{tex}\Delta t_2=|t_{mean}-t_2|= |92-91|=1{/tex}

{tex}\Delta t_3=|t_{mean}-t_3|= |92-92|=0{/tex}

{tex}\Delta t_4=|t_{mean}-t_4|= |92-95|=3{/tex}

Let’s  calculate the mean  absolute error:

{tex}\Delta t_{mean}={ \Delta t_1+ \Delta t_2+ \Delta t_3+ \Delta t_4\over 4}{/tex}

{tex}{2+1+0+3\over 4}= 1.5{/tex}{tex}\approx 2{/tex}

Therefore,  the reported  mean  time should  be  92 ± 2s

Answered by Payal Singh (Jun 24, 2017 5:42 p.m.)
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Surface tension

Posted by Harsh Vikram Singh (Jun 23, 2017 8:11 p.m.) (Question ID: 6130)

1. the tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area.

Answered by Saurav Kumar (Jun 23, 2017 9:53 p.m.)
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Two charges +10mew coulamb and -10 new column are located at distance of 2 cm from each other. Calculate the electric field at point lying on the axial line at a distance of 60 cm from the centre of the dipole

Posted by Anjali Rani (Jun 18, 2017 9:14 p.m.) (Question ID: 6014)

1.What are polar and axial vectors?

Give examples of each if possible.

Posted by Rohan P (Jun 18, 2017 3:13 p.m.) (Question ID: 5998)

• In physics, a polar vector is a vector such as the radius vector r that reverses sign when the coordinate axes are reversed. Polar vectors are the type of vector usually simply known as "vectors." In contrast, pseudovectors (also called axial vectors) do not reverse sign when the coordinate axes are reversed. Examples of polar vectors include r, the velocity vector v, momentum p, and force F. The cross product of two polar vectors is a pseudovector

Answered by Payal Singh (Jun 18, 2017 5:01 p.m.)
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g1 = g (1 - 2 / 291)^ 1/ 2

Posted by Namrata Pandey (Jun 13, 2017 11:45 a.m.) (Question ID: 5884)

difference between qualitative and quntitative analysis

Posted by Shaanthosh Shaanthosh (Jun 12, 2017 8:15 p.m.) (Question ID: 5879)

•  Qualitative Analysis Quantitative Analysis Qualitative Analysis is used when the researcher wishes to analyze data that are subjective and not numerical. In the quantitative analysis the data is analyzed through statistical means. This focuses on descriptive data. This focuses on numerical data. This can be used to explore attitudes, behavior, nature of experience, etc. This can be used for presenting percentages or any form of statistically significant data.
Answered by Payal Singh (Jun 12, 2017 9:57 p.m.)
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explain the two principle thruts in physics with example

Posted by Shaanthosh Shaanthosh (Jun 12, 2017 8:12 p.m.) (Question ID: 5878)

• Two principles thrusts in the study of Physics are

• Unification which means explaining different physical phenomena by using few laws and concepts. Example: Electricity, magnetism and light are different phenomena and have different laws of physics for each of them. These are unified under theory of electromagnetism; all these three phenomena can be explained from this theory of electromagnetism.
• Reductionism which means explaining complex phenomena by breaking them into smaller constituents and studying simpler parts.

Example: A complex music can be broken down to simple sine waves so that we can make the music piece from the simple tones.

Answered by Payal Singh (Jun 13, 2017 7:27 a.m.)
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a football is picked vertically upwards from the ground and a student gazing out for windows sees it moving upwards pass her at 5m/s the window is 15m about the ground

<hr>

A=how high does the football above the ground

<hr>

B=how much time does it take to go from the ground to its highest point

Posted by Uday Bhardwaj (Jun 10, 2017 12:53 p.m.) (Question ID: 5829)

• let the initial velocity of football is u m/sec motion from ground to window

v=5m/sec

h=15m

v2 -u2 =2gh

=> 25 -u2 = 2*(-10)*15

=> u2=325

=u = {tex}\sqrt {325} = 5\sqrt{13}{/tex}m/s

A)motion from window to maximum height

v2-u= 2as

Here v is final velocity of ball = 0m/s

u is initial velocity of ball = 5m/s

a is acceleration due to gravity = -10 as it is going upward

s is distance traveled by it = ?

So,

=> 0 - 25 = 2*(-10)*h

=> -25 = -20h

=> h = {tex}{-25\over -20}= {5\over 4}{/tex}

Total height = 15 + {tex}{5\over 4} = {65\over 4}{/tex}m

B)motion from ground to max height

u= {tex}5\sqrt{13}{/tex}

v=0

v=u-gt

t={tex}{5\sqrt {13}\over 10}= {\sqrt {13}\over 2} sec{/tex}

Answered by Payal Singh (Jun 10, 2017 2:40 p.m.)
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A particle travels in a straight line such that for a short time it's motion is described by v=4/a if v=6m/s when 4t=2 determine the particle acceleration when t=3second

Posted by Uday Bhardwaj (Jun 10, 2017 12:46 p.m.) (Question ID: 5827)

How static friction provides centripetal acceleration

Posted by Pfff Xy (Jun 09, 2017 2:41 p.m.) (Question ID: 5797)

• A car in a steady turn has a centripetal acceleration. There is an inertial force associated with every acceleration acting in the opposite direction and in this case it is the centrifugal force. The friction at the tires arises as a centripetal force to match the centrifugal force.

Answered by Shweta Gulati (Jun 10, 2017 1:14 a.m.)
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a stone is dropped from the top of the tower when it crosses a point 5metre below the top another stone is let fall from a point 25 metre below the top.both stones reached the tower simultaneously. find the height of tower

Posted by Uday Bhardwaj (Jun 09, 2017 1:51 p.m.) (Question ID: 5796)

• Let height of tower be 'h'

Time taken for 1st stone to reach ground = {tex}\sqrt{2h\over g}{/tex}

{tex}\left[ s = ut+ {1\over 2}at^2 ;h = {1\over 2}gt^2\right]{/tex}

Time taken for the first stone to be travel 5 m from top = {tex}\sqrt{2\times 5\over g}{/tex}

Time taken for 2nd stone to reach ground from a point (h−25)m above the ground = {tex}\sqrt{2(h-25)\over g}{/tex}

So,

{tex} \sqrt{2h\over g} -\sqrt{2\times 5\over g} = \sqrt{2(h-25)\over g}{/tex}

{tex}=> \sqrt{2h} -\sqrt{10} = \sqrt{2(h-25)}{/tex}

Squaring both sides

=> 2h + 10 - {tex}2\sqrt {20h}= {/tex}2h -50

=> {tex}\sqrt{20h} = 30{/tex}

Sqauring both sides

=> 20h = 900

=> h = 45

Answered by Payal Singh (Jun 09, 2017 6:16 p.m.)
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How sometimes technology gives rise to new physics at other times physics generates new technology??

Posted by Gourav Pandey (May 20, 2017 3:13 p.m.) (Question ID: 5394)

• Ans. The connection between physics, technology and society can be seen in many examples. The discipline of thermodynamics arose from the need to understand and improve the working of heat engines. The steam engine is inseparable from the Industrial Revolution in England in the eighteenth century, which had great impact on the course of human civilisation. Sometimes technology gives rise to new physics; at other times physics generates new technology

We can understand this by some examples :

• The wireless communication technology that followed the discovery of the basic laws of electricity and magnetism in the nineteenth century.

• Development of Alternative Energy Resources : A most significant area to which physics has and will contribute is the development of alternative energy resources. The fossil fuels of the earth are ending fast and there is an urgent need to discover new and affordable sources of energy. Considerable progress has already been made in this direction. For example : Conversion of solar energy, geothermal energy into electricity.

• Silicon Chip Technology : Yet another important example of physics giving rise to technology is the silicon chip, that triggered the computer revolution in the last three decades of the twentieth century.
Answered by Naveen Sharma (May 20, 2017 3:50 p.m.)
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What are the three region of phenomenal progress in physics in the last few centuries??

Posted by Gourav Pandey (May 20, 2017 1:08 p.m.) (Question ID: 5391)

Why it is said that science is ever dynamic.  There is no final theory in science and no unquestioned authority among scientist..

Posted by Gourav Pandey (May 19, 2017 4:57 p.m.) (Question ID: 5380)

• Ans. The fact that we do not have a final theory in science is testament to our very limited understanding of the world around as well as within us. We do not have a complete sense of apprehension about most (if not all) of the various facets of science, like the following.

• what causes life?
• are we alone In space?
• what is the final number of elements in our universe ?

Many such questions plague the minds of scientists today and until all such queries are dealt with we will never have a full sense of everything. Now, even if we do happen to find the answers to everything then how do we now that there aren't any other questions left.

In other words do we even completely know what lies phenomena lies uncovered for us to decipher its mechanism. It seems almost impossible to demystify all of them, let alone the unknown stuff.

So, it might seem a bit pessimistic but it is almost certain that we will never have a final theory of science there are bound to be a few exceptions, but that is the fun of it all. The world would be a dull place without all its mysteries (for us to solve).
Answered by Naveen Sharma (May 19, 2017 5:17 p.m.)
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How theory and experiment go hand in hand in physics and help each other's progress

Posted by Gourav Pandey (May 19, 2017 4:52 p.m.) (Question ID: 5379)

• Every experiment, calculation, result and prediction starts and ends with theory. Theory and experiment go hand in hand.

Theory makes predictions and motivate experiments. Experimental results are used to update, improve and validate the framework that scientists work within.

The models are reassessed under the light of the new data. The new information then comes full circle by helping to determine which experiments are conducted next. By knowing where the gaps in knowledge are – where  theory needs more information – scientists can better decide which questions to ask and which experiments to run next.

Answered by Payal Singh (May 19, 2017 5:14 p.m.)
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What is scope of physics and exitement???

Posted by Gourav Pandey (May 19, 2017 1:13 p.m.) (Question ID: 5376)

What is hypothesis, axiom and models

Posted by Gourav Pandey (May 19, 2017 10:09 a.m.) (Question ID: 5372)

• A hypothesis is a supposition without assuming that it is true. It would not fair to ask anybody to prove the universal law of gravitation, because it cannot be proved. It can be verified by experiments.
• An Axiom is self-evident truth
•  A Model is a theory proposed to explain observed phenomena.
Answered by Payal Singh (May 19, 2017 11:04 a.m.)
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What is theory? And its example..

Posted by Gourav Pandey (May 18, 2017 7:53 p.m.) (Question ID: 5365)

• Theory is a set of statements or principles devised to explain a group of facts or phenomena.

Most theories that are accepted by scientists have been repeatedly tested by experiments and can be used to make predictions about natural phenomena.

Answered by Payal Singh (May 19, 2017 6:30 a.m.)
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Tell me any project based on the laws of motion

Posted by manoj ramna (May 17, 2017 7:15 p.m.) (Question ID: 5355)

1. How elastic spring forces arise?
Posted by lochan soni (May 14, 2017 11:29 a.m.) (Question ID: 5305)

• The elastic spring force arise due to the net attraction/repulsion between the neighboring atoms of the spring when the spring is elongated/compressed.

This net attraction/ repulsion can be traced to the sum of electric forces between the charged constituents of the atoms.

Answered by Payal Singh (May 15, 2017 7:46 a.m.)
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1. Give a method to measure size of the atom using Avogadro’s hypothesis?

Posted by lochan soni (May 14, 2017 11:28 a.m.) (Question ID: 5304)

• By Avogadro's hypothesis, the actual volume occupied by the atoms in one gram of a substance is 2/3rd of the volume occupied by 1 gram of the substance.

Let us consider a sample of a substance of mass m and volume V. If M is its molecular weight and Avogadro number is N, then

Number of atoms in the given sample = {tex}{N\over M}× m = {Nm\over M}{/tex}

let each atom is a sphere of radius r..

So

Actual volume of the atoms in the given sample = {tex}{Nm\over M}×{4\over 3}\pi r^3{/tex}

{tex}{Nm\over M}×{4\over 3}\pi r^3 = {2\over 3}V{/tex}

If {tex}\rho{/tex} is density of substance . Then

{tex}\rho = {m\over V} \\=> V = {m\over \rho}{/tex}

{tex}=> {Nm\over M}×{4\over 3}\pi r^3 = {2\over 3}{m\over \rho}{/tex}

{tex}r = \left ({M\over 2 \pi N\rho }\right )^{1\over 3}{/tex}

Knowing values of M,N and {tex}\rho{/tex}

We can find radius

Answered by Payal Singh (May 19, 2017 7:48 a.m.)
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1. The diameter of a thin wire measured with screw gauge, the value are 2.04mm,2.06mm,2.06mm,2.08mm,2.07mm,2.05mm. find the average diameter of wire, absolute error, mean absolute error, relative error, and percentage error.
Posted by lochan soni (May 14, 2017 11:27 a.m.) (Question ID: 5303)

1. Find whether the formula given below in dimensionally correct.

FS = 1/2mv2 – 1/2mu2

Posted by lochan soni (May 14, 2017 11:27 a.m.) (Question ID: 5302)

• ofcourse the above equation is dimensionally correct

[F][S]=[m][v]2-[m][u]2

[MLT-2][L]=[M][LT-1]2-[M][LT-1]2

[ML2T-2]=[ML2T-2]+ [ML2T-2]

WE know subraction of same dimensions givse the same dimension

so

[ML2T-2]=[ML2T-2]

L.H.S.=R.H.S

hence the above equation is dimensionally correct.

Answered by Ankit Kumar (May 31, 2017 5:29 p.m.)
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• Mebsion its measures.

Answered by Nikhil Malik (May 16, 2017 6:02 p.m.)
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1. Find the expression for centripetal force if it depends upon mass of the body, and the radius of the circular path?
Posted by lochan soni (May 14, 2017 11:27 a.m.) (Question ID: 5301)

• The centripetal force, F acting on a particle moving uniformly in a circle depend upon the mass (m), velocity (v) and radius (r) of the circle.

The formula for F using the method of dimensions.

Let F = k ma vb rc…..... (i)

Where, k is the dimensionless constant of proportionality, and a, b, c are the powers of m, v, r respectively.

On writing the dimensions of various quantities in (i),

we get

[M1L1T-2] = Ma [LT-1]bLc

=> [M1L1T-2] = MaLbLcT-b

=> [M1L1T-2] = MaLb+c T-b

on comparing both sides we get

a = 1

b+c = 1

-b = -2 => b = 2

Then c = -1

Onputting these values in (i),

we get

F = k m1 v2 r-1

Or

{tex}F = k {mv^2\over r}{/tex}

This is the required relation for centripetal force.

Answered by Payal Singh (May 19, 2017 8:06 a.m.)
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1. What do you understand by fundamental quantities and units?
Posted by lochan soni (May 14, 2017 11:27 a.m.) (Question ID: 5300)

• The quantities that do not depend on any other physical quantity for their measurement are known as fundamental quantities.These quantities do not take support of other physical quantities for its measurement. There are only 7 physical quantities.
• Afundamental unit is a unit of measurement for a measurable physical property from which every other unit for that quantity can be derived.Fundamental units are also known as base units.
Answered by Payal Singh (May 15, 2017 2:40 p.m.)
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1. What are the advantage of SI system of units.?
Posted by lochan soni (May 14, 2017 11:27 a.m.) (Question ID: 5299)

• The International System of Units, symbolized SI, is the simplified modern version of the metric system.

• No conversions (only one unit for each quantity)
• No numbers to memorize (derived units are defined without numerical factors)
• No fractions (decimals only)
• No long rows of zeros (prefixes eliminate them) Only 30 individual units (compared to hundreds of traditional units)
• Easy to pronounce and write (short names; simple letter symbols)
• Based on natural standards (size of Earth, water, laws of physics)
• Coherent system (symbols can be manipulated algebraically)
• World standard (even traditional U.S. units are defined by it)
Answered by Payal Singh (May 16, 2017 6:37 p.m.)
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1. Meter is well defined in term of wavelength and time in terms of periods of radiation. Why?
Posted by lochan soni (May 14, 2017 11:26 a.m.) (Question ID: 5298)

1. How the distance of nearest star can be determine?
Posted by lochan soni (May 14, 2017 11:26 a.m.) (Question ID: 5297)

1. Explain the method to determine the size of moon?
Posted by lochan soni (May 14, 2017 11:26 a.m.) (Question ID: 5296)

• He was actually timing how long between the entry and exit of the darker (umbral) shadow. Which to him appeared to be around 2.6 hours. Next, he compared this with the time it takes the moon to move a distance equal to it’s diameter. In the previous article we determined that this was about 1 hour. So he’s left with two numbers:

• time it takes the moon to travel 1 moon diameter = 1 hour
• time it takes the moon to travel 1 earth diameter  = 2.6 hours

How could we figure out the size of the moon from this?

If the times were equal than it would imply that the moon is the same size as the earth. However the time of a lunar eclipse is much longer, which means the earth must be larger. How much larger? We need to setup a basic proportion:

time #1 / time #2 = moon diameter / earth diameter

1 / 2.6 = moon diameter / earth diameter

This led him to claim that the earth was about 8/3 the diameter of the moon. This is pretty close to the actual difference: the earth is about 3.7 times bigger than the moon. The main reason he underestimated was because the umbral shadow is narrower than the earth.

<h2 data-reactid="471">Actual size of the moon</h2>

We now know the relative size of the moon compared to earth. We also know the actual size of the earth from a previous calculation. Finally we can determine the approximate size of the moon!

moon diameter = earth Diameter / 3.7

moon diameter = 12742/3.7 = 3444 km

This is very close to the actual diameter of the moon: 3474.8 km

Answered by Mukul Tanwar (May 14, 2017 10:04 p.m.)
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1. Explain the echo to find the distance of moon ?
Posted by lochan soni (May 14, 2017 11:25 a.m.) (Question ID: 5295)

• In this method, laser beam is used in place of sound waves to find the distance of moon from earth.

A laser beam is sent towards moon. This transmitted beam from earth is received back on earth after reflection from the moon.

Suppose the time interval between transmission and reception of the beam is t, the velocity of beam in air/vacuum is c and s is the distance of moon from earth, Then

Distance=Velocity x time

2s=c x t or

s= {tex} {ct \over 2}{/tex}

Answered by Payal Singh (May 19, 2017 8:12 a.m.)
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