Tag: physics

Questions Related to physics

The maximum load a wire can with stand without breaking, when it is stretched to twice of its original length, will:

elastic energy properties of material substances elasticity properties of matter physics

  1. be half

  2. be four time decreased

  3. be double

  4. remain same

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Correct Option: D
Explanation:

the maximum load a wire can with stand without breaking it is stretched to twice of its original length is remain same$.$

Hence,
option $(D)$ is correct answer.

A uniform wire of length L and radius r is twisted by a angle $ \angle \alpha$. If modulus of rigidity of the wire is $ \eta  $, then the elastic potential energy stored in wire, is

elastic energy properties of material substances elasticity properties of matter physics

  1. $ \frac{\pi \eta r^{4}\alpha }{2L^{2}} $

  2. $ \frac{\pi \eta r^{4}\alpha^{2} }{4L} $

  3. $ \frac{\pi \eta r^{4}\alpha }{4L^{2}} $

  4. $ \frac{\pi \eta r^{4}\alpha^{2} }{2L} $

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Correct Option: B

The length of an elastic string is $x$ metre when the tension is $8\ N$. Its length is $y$ metre when the tension is $10\ N$. What will be its length, when the tension is $18\ N$?

elastic energy properties of material substances elasticity properties of matter physics

  1. $2x + y$

  2. $5y - 4x$

  3. $7y - 5x$

  4. $7y + 5x$

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Correct Option: B
Explanation:

Let, original length of the spring is L metre and, Y = $\dfrac { F.L }{ A.l } $

Now, when F = 8N, and l = (x - l)m then, $Y=\dfrac { 8.L }{ A.\left( x-L \right)  } \quad \longrightarrow (I)$
and when F=10N, and l = (y - l)m then, $y=\dfrac { 10.L }{ A.\left( y-L \right)  } m\quad \longrightarrow (II)$
From equation (I) and (II) we get,
$\dfrac { 8L }{ A\left( x-L \right)  } =\dfrac { 10L }{ A\left( y-L \right)  } $
or,  $8\left( y-L \right) =10\left( x-L \right) $
or,    $4y-4L=5x-5L$
or,                $L=5x-4y$
When, F=18N,
Let, length of the wire will be Z metre.
$\therefore \quad Y=\dfrac { 18.L }{ A.\left( Z-L \right)  } \quad \longrightarrow (III)$
From equation (I) and (III) we get,
$\dfrac { 8L }{ A\left( x-L \right)  } =\dfrac { 18L }{ A\left( Z-L \right)  } $
or,  $9\left( x-L \right) =4\left( Z-L \right) $
or,  $4Z=9x-9L+4L$
            $=9x-5L$
            $=9x-25x+20y$    [putting value of L]
or,  $Z=5y-4x$


If 1 kg wt = 10 N, the value of gravitational intensity will be 

physics dynamics - explaining motion system of unit summary of si units system of units

  1. $\displaystyle 10{ m }/{ { s }^{ 2 } }$

  2. $\displaystyle \frac { 1 }{ 10 } { m }/{ { s }^{ 2 } }$

  3. $\displaystyle 1{ m }/{ { s }^{ 2 } }$

  4. $\displaystyle \frac { 1 }{ 100 } { m }/{ { s }^{ 2 } }$

Show answer
Correct Option: A
Explanation:

If $1\,kg\,wt=10\,N=F$

Then gravitational intensity is given by,
$g=\dfrac Fm$
$=\dfrac{10 }{1}=10 m/s^2$

The magnetic field flux is expressed in

physics dynamics - explaining motion system of unit summary of si units system of units

  1. Dynes

  2. Oersted

  3. Gauss

  4. Weber

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Correct Option: D
Explanation:

Magnetic Flux is defined as the number of magnetic field lines passing through a given closed surface. It gives the measurement of the total magnetic field that passes through a given surface area. S.I. unit of magnetic flux is Weber $(Wb)$.

Which of the following class of forces is different from others?

physics dynamics - explaining motion system of unit summary of si units system of units

  1. Pulling of a cart

  2. Stretching of a coiled spring

  3. Kicking of a football

  4. Electrical force

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Correct Option: D
Explanation:

Pulling of a cart, stretching of a coiled spring and kicking of a football take place due to contact forces. A contact force is any force that requires contact to occur. But electrical force is a non contact force which acts on an object without coming physically in contact.

Which kind of waves are produced by supersonic jet planes?

physics dynamics - explaining motion system of unit summary of si units system of units

  1. Shock waves

  2. Seismic waves

  3. Infrasonic waves

  4. Infrared waves

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Correct Option: A
Explanation:

The waves produces by the supersonic jet planes are shock waves. When a wave moves faster than the local speed of sound in a fluid, it is a shock wave.

100 square millimetres ($mm^2$ )= ________ square centimetre($cm^2$).

physics dynamics - explaining motion system of unit summary of si units system of units

  1. $100$

  2. $10$

  3. $1$

  4. $0.1$

Show answer
Correct Option: C
Explanation:
1 Sq. Centimeter = 100 Sq. Millimeters
1 Sq. Millimeter = 0.01 Sq. Centimeter

_______ square centimetres = $1$ square decimetre ($dm^2$ )

physics dynamics - explaining motion system of unit summary of si units system of units

  1. $100$

  2. $10$

  3. $1000$

  4. $0.1$

Show answer
Correct Option: A
Explanation:

$1\ cm=0.1\ dm$ or $10\ cm=1\ dm$

Thus, $1\ dm\times  1\ dm=10\ cm\times 10\ cm$
So, $1\ dm^2=100\ cm^2$

Which of the following is used as SI prefixes:

physics dynamics - explaining motion system of unit summary of si units system of units

  1. Micro

  2. Mica

  3. Mikro

  4. Maca

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Correct Option: A
Explanation:

Micro is a prefix used in defining some units.  Whenever the word micro is attached as a prefix to an SI unit,  it means it is one million times smaller than that unit. For example, 1 micrometre is one millionth part of a metre. Rest all other options are not   prefixes