Tag: physics

Questions Related to physics

The velocity of the transverse waves in a wire of density $8000kg/m^3$ is $300 m/s$. The tensile stress in the wire is then

forces on solids elastic and plastic substances forces and matter properties of matter physics

  1. $7.2\times10^8 N/m^2$

  2. $6.8\times10^8 N/m^2$

  3. $5.2\times10^8 N/m^2$

  4. $8.4\times10^8 N/m^2$

Show answer
Correct Option: A
Explanation:

Given density = 8000 $kg/{ m }^{ 3 }$ and velocity =300 m/s

Also we know velocity of transverse wave  $\text{V}=\sqrt { \dfrac { T }{ \mu  }  } \text{where T= tension and}\quad \mu =\text{mass per unit lenght}\quad =\dfrac { m }{ L } \quad $
also $\text{Density}\quad \rho =\dfrac { mass }{ Area\times Lenght } \ \rho \times A=\dfrac { m }{ L } $
$\text{Tension T}=\rho A{ V }^{ 2 }$
We know stress $\sigma =\dfrac { Force }{ Area } =\dfrac { Tension }{ Area } =\dfrac { { V }^{ 2 }\rho A }{ A } ={ V }^{ 2 }\rho $
${ 300 }^{ 2 }\times 8000=7.2\times { 10 }^{ 8 }\dfrac { N }{ { m }^{ 2 } } $ 

An external force of $10\ N$ acts normally on a square area of each side $50\ cm$. The stress produced in equilibrium state is

forces on solids elastic and plastic substances forces and matter properties of matter physics

  1. $10\ N/m^{2}$

  2. $20\ N/m^{2}$

  3. $40\ N/m^{2}$

  4. $50\ N/m^{2}$

Show answer
Correct Option: C

The length of wire is increased by $0.06\%$ by a load of $40N$ whose tensile modulus is $20\times10^{10}N/M^2$.The subjected stress is 

forces on solids elastic and plastic substances forces and matter properties of matter physics

  1. $12\times10^{10}N/m^2$

  2. $1.2\times10^{8}N/m^2$

  3. $120N/m^2$

  4. $1.25\times10^6N/m^2$

Show answer
Correct Option: B
Explanation:

$\cfrac{\triangle l}{l}\times 100=0.06$

$\implies \cfrac{\triangle l}{l}=\cfrac{0.06}{100}$
Now stress $=\cfrac{20\times 10^{10}\times 0.06}{1000}\=1.2\times 10^8\ N /m^2$

According to $C.E$ van der Waal, the interatomic potential varies with the average interatomic distance $(R)$ as 

forces on solids elastic and plastic substances forces and matter properties of matter physics

  1. $R^{-1}$

  2. $R^{-2}$

  3. $R^{-4}$

  4. $R^{-6}$

Show answer
Correct Option: D
Explanation:

According to the relation

$ V(r)=\dfrac{-3}{4}\dfrac{{{\alpha }^{2}} _{0}l}{{{(4\pi {{\varepsilon } _{0}})}^{2}}{{R}^{6}}} $

$ V(r)\propto \dfrac{1}{{{R}^{6}}} $

$ V(r)\propto {{R}^{-6}} $


Overall changes in volume and radii of a uniform cylindrical steel wire are $0.2\% $ and $0.002\%$ respectively when subjected to some suitable force. Longitudinal tensile stress acting on the wire is $\left( {Y = 2.0 \times {{10}^{11}}N{m^{ - 2}}} \right)$

forces on solids elastic and plastic substances forces and matter properties of matter physics

  1. $3.2 \times {10^9}N{m^{ - 2}}$

  2. $3.2 \times {10^7}N{m^{ - 2}}$

  3. $3.6 \times {10^9}N{m^{ - 2}}$

  4. $3.6 \times {10^7}N{m^{ - 2}}$

Show answer
Correct Option: C

A steel wire has an ultimate strength of above $2.0 \times 10 ^ { 7 } \mathrm { kg } - \mathrm { w } \mathrm { J } / \mathrm { m } ^ { 2 }$ . How large a load can a
0.7$\mathrm { cm }$ in diameter steel wire hold before breaking?

forces on solids elastic and plastic substances forces and matter properties of matter physics

  1. $700 \mathrm { kg } - \mathrm { wt }$

  2. $770 \mathrm { kg } - \mathrm { wt }$

  3. $300 \mathrm { kg } - \mathrm { wt }$

  4. None

Show answer
Correct Option: A

If equal and opposite forces applied to a body tend to elongate it, the stress so produced is called

forces on solids elastic and plastic substances forces and matter properties of matter physics

  1. Tensile stress

  2. Compressive stress

  3. Tangential stress

  4. Working stress

Show answer
Correct Option: A

A rubber cord 10 m is suspended vertically . How much does is stretch under its own weight (density of rubber is $1500kg{ m }^{ -3 },Y=5\times { 10 }^{ 8 }{ Nm }^{ -2 },g={ ms }^{ -2 }$)

forces on solids elastic and plastic substances forces and matter properties of matter physics

  1. $15\times { 10 }^{ -4 }m\quad $

  2. $7.5\times { 10 }^{ -4 }m\quad $

  3. $12\times { 10 }^{ -4}m $

  4. $25\times { 10 }^{ -4 }m\quad $

Show answer
Correct Option: B

A copper wire of $1mm$ diameter is stretched by applying a force on $10N$. Find the stress in the wire.

forces on solids elastic and plastic substances forces and matter properties of matter physics

  1. $1.273\times 10^7N/m^2$

  2. $1.373\times 10^7N/m^2$

  3. $1.473\times 10^7N/m^2$

  4. $1.573\times 10^7N/m^2$

Show answer
Correct Option: A

When the inter molecular distance increases due to tensile force, then 

forces on solids elastic and plastic substances forces and matter properties of matter physics

  1. There is no force between the molecules

  2. There is a repulsive force between the molecules

  3. There is an attractive force between the molecules

  4. There is zero resultant force between the molecules

Show answer
Correct Option: C