Tag: physics

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Questions Related to physics

Multiple choice physics electric current and its effects electric fuse electrical fuse and mcb fuse

An electric iron draws a current of 15 A from a 220 V supply. What is the cost of using iron for 30 min everyday for 15 days if the cost of unit (1 unit $=$ 1 k W hr) is 2 rupees?

  1. Rs. 49.5

  2. Rs. 60

  3. Rs. 40

  4. Rs. 10
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$I=15 A, V=220 V, t=30 min$
$Energy=P\times t=VIt$
$=220\times 15\times \frac {30}{60}\times 15$
$=3300\times \frac {1}{2}\times 15 W hr$
$=3.3\times kW\times 7.5 hr$
$=24.75 kW hr$
$Cost=24.75\times 2=Rs. 49.50$

Multiple choice physics electric current and its effects electric fuse electrical fuse and mcb fuse

The parameter irrelevant for an electric fuse wire is 

  1. its radius.

  2. its specific resistance.

  3. current flowing through it.

  4. its length.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For fuse wire expression for heat produced is given by eq. is  $H = \dfrac{I^2 \rho}{2 \pi ^2r^3}$
Hence, it is independent on length of fuse wire. Thus, the parameter irrelevant for an electric fuse wire is its length.

Multiple choice physics mechanical properties of solids applications of elasticity elastic energy properties of matter

State whether true or false :
The hollow shaft is much stronger than a solid shaft of same mass, same length and same material.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Modulus of elasticity = $\dfrac { stress }{ strain } $     and, stress = $\dfrac { Force }{ Area } $

$\therefore $  Elasticity $\alpha \dfrac { 1 }{ Area } $
As follow shaft, so, elasticity of the follow shaft is more than a solid one. As elasticity measures rigidity. So, hollow shaft is stronger.

Multiple choice physics mechanical properties of solids applications of elasticity elastic energy properties of matter
 A cable that can support a load of 1000 N is cut into equal parts. the maximum load that can be supported by the either part is:-

  1. 1000 N

  2. 2000 N

  3. 500 N

  4. 250 N
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Maximum load supported by the cable is directly proportional to the breaking stress.

Since,

Breaking stress = F / A

where F is the force and A is the cross-sectional area.

As we see that the breaking stress is independent of the length of the cable. So, if the cable is cut in two equal parts, the maximum load that can be supported by either parts of the cable remain the same as before.

Multiple choice physics mechanical properties of solids applications of elasticity elastic energy properties of matter

State whether true or false :
The metal used in construction of a bridge should have high Young's modulus.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Young's modulus measures modulus of elasticity of a material. 

Elasticity defines rigidity of the material. 
So, for construction, we need metals which have high elasticity i.e. high young's modulus.

Multiple choice physics mechanical properties of solids applications of elasticity elastic energy properties of matter

A silver wire of length $10 $ metre and cross-sectional area $10^{-8} m^{2}$ is suspended vertically and a weight of $10 N$ is attached to it. Young's modulus of silver and its resistivity are $7 \times 10^{10} N/m^{2}$ and $1.59 \times 10^{8} N/m^{2}$ \Omega - m$ respectively. The increase in its resistance is equal to:-

  1. $0.0455 \Omega$

  2. $0.455 \Omega$

  3. $0.91 \Omega$

  4. $0.091 \Omega$
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice physics mechanical properties of solids applications of elasticity elastic energy properties of matter

In the system shown in figure pulley is smooth. String is massless and inextensible. The acceleration of the system a, tensions ${T} _{1}\ and {T} _{1}\left (g=10{m/s}^{2}\right)$ are 

  1. $\dfrac { 20 }{ 3 } { m/s }^{ 2 },\dfrac { 50 }{ 3 } N,\dfrac { 60 }{ 3 } N$

  2. $\dfrac { 10 }{ 3 } { m/s }^{ 2 },\dfrac { 100 }{ 3 } N,\dfrac { 60 }{ 3 } N$

  3. $\dfrac { 20 }{ 3 } { m/s }^{ 2 },\dfrac { 100 }{ 3 } N,\dfrac { 60 }{ 3 } N$

  4. $\dfrac { 20 }{ 3 } { m/s }^{ 2 },\dfrac { 100 }{ 3 } N,\dfrac { 50 }{ 3 } N$
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice physics mechanical properties of solids applications of elasticity elastic energy properties of matter

A stone of mass 'm' s projected from a rubber catapult of length 'l' and cross-sectional area A stretched by an amount 'e'. If Y be the young's modulus of rubber then the velocity of projection of stone?

  1. $Y \sqrt {\dfrac{Ae^2}{lm}}$

  2. $ \sqrt {\dfrac{Ae^2}{lm}}$

  3. $Y \sqrt {\dfrac{YAe^2}{lm}}$

  4. $Y \sqrt {\dfrac{YAe^4}{lm}}$
Reveal answer Fill a bubble to check yourself
C Correct answer