Tag: physics

Questions Related to physics

A mass of $0.5$ kg is suspended from wire, then lemgth of wire increase by $3$ mm then find out work done:

physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. $4.5 \times {10^{ - 3}}J$

  2. $7.3 \times {10^{ - 3}}J$

  3. $9.3 \times {10^{ - 2}}J$

  4. $2.5 \times {10^{ - 2}}J$

Show answer
Correct Option: A

The work done by all the forces (external and internal) on a system equals the change in 

physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. Total energy

  2. Kinetic energy

  3. Potential energy

  4. none of these

Show answer
Correct Option: B,C

In a hydroelectric power plant ___ energy is converted into ____ energy.

physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. Chemical into electrical

  2. Chemical into mechanical

  3. Mechanical into electrical

  4. Electrical into mechanical

Show answer
Correct Option: C
Explanation:

In hydroelectric power plant following sequence of energy transformation take place, 

Kinetic energy of water to potential energy of water to mechanical energy of turbine to electric energy through generator.
So among the options given best possible answer is option C.

A single conservative force F(x) acts on a $1$ kg particle that moves along the x-axis. The potential energy U(x) is given by $U(x) = 10+(x-1)^2$ Where x is in meters. At x =$2$ m, the particle has a kinetic energy of $8$ Joules. Then the mechanical energy of particle is

physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. $18$ J

  2. $19$ J

  3. $20$ J

  4. $10$ J

Show answer
Correct Option: A

If $484J$ of energy is spent in increasing the speed of a wheel from $60rpm$ to $360\ rpm$, the $M.I$ of the wheel is

physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. $1.6\ kg\ m^{2}$

  2. $0.3\ kg\ m^{2}$

  3. $0.7\ kg\ m^{2}$

  4. $1.2\ kg\ m^{2}$

Show answer
Correct Option: C
Explanation:

$\begin{array}{l} { \eta _{ 1 } }=60rpm=\dfrac { { 60 } }{ { 60 } } rps=1rps \ \therefore { w _{ 1 } }=2r{ \eta _{ 1 } }=2\pi  \ { \eta _{ 2 } }=\dfrac { { 360 } }{ { 60 } } rpm=6rps \ { w _{ 2 } }=2\pi { \eta _{ 2 } }=12\pi  \end{array}$

484 joule of energy is spent in increasing.
$\begin{array}{l} \frac { 1 }{ 2 } Iw _{ 2 }^{ 2 }-\dfrac { 1 }{ 2 } Iw _{ 1 }^{ 2 }=484 \ \dfrac { I }{ 2 } \left( { { w _{ 2 } }+{ w _{ 1 } } } \right) \left( { { w _{ 2 } }-{ w _{ 1 } } } \right) =484 \ \dfrac { I }{ 2 } \left( { 12\pi +2\pi  } \right) \left( { 12\pi -2\pi  } \right) =484 \ I\, \, 14\pi .10\pi =484 \ I=\dfrac { { 484\times 2 } }{ { 140\times { \pi ^{ 2 } } } } =\dfrac { { 484\times 2 } }{ { 140\times 9.86 } }  \ =0.7\, \, kg\, \, { m^{ 2 } } \end{array}$
Option C.

State True or False :
Coal forms from plants. 

physics sources of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Coal is fossil fuel formed from remains of plants that lived and died millions of years ago.

Which is a non-renewable energy resource?

physics sources of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy production of electricity from solar energy

  1. coal

  2. solar

  3. tides

  4. wind

Show answer
Correct Option: A
Explanation:

All fossil fuels are non- renewable source of energy. Since coal is a fossil fuel so, it is a non renewable resource.

Why do we hear more clearly in a room with curtains than in a room without curtains?

physics study of sound reverberation applications of reflection of sound multiple reflection of sound and reverberation applications of ultrasound

  1. sound is absorbed by the curtains.

  2. less reverberation

  3. a and b

  4. none

Show answer
Correct Option: A
Explanation:

We hear more clearly in a room with curtains than of that in a room without curtains because curtains act as a good sound absorbent. So, they absorb the sound produced in the room and thus, prevent unwanted echo of sound due to refraction. Otherwise, the inter lapping of sounds would be most undesirable as we won't be able to hear clearly.

_________ is a device which is based on multiple reflection and isused for sending amplified sound in a particular direction.

physics study of sound reverberation applications of reflection of sound multiple reflection of sound and reverberation applications of ultrasound

  1. Bulb horn

  2. Megaphone

  3. Ear trumpet

  4. all

Show answer
Correct Option: B
Explanation:

Megaphone is based on multiple reflection of sound. It is a horn shaped tube designed to send amplified sound in a particular direction. It is also called Loud hailer.

Which of the following device does not work on the multiple reflections of sound waves?

physics study of sound reverberation applications of reflection of sound multiple reflection of sound and reverberation applications of ultrasound

  1. stethoscope

  2. hydrophone

  3. soundboard

  4. megaphone

Show answer
Correct Option: B
Explanation:

Stethoscope is a medical diagnostic instrument based on multiple reflection of sound waves.
This is used by doctors for listening to the sounds produced inside the body.
Sound board is a concave rigid surface which is placed behind the speaker in a big hall so that his words can be heard clearly even by the people sitting away from the stage.