Tag: physics

Questions Related to physics

In a beaker containing liquid, an ice cube is floating. When ice melts completely, the level of liquid rises. Then the density of the liquid is:

physics upthrust in fluids, archimedes' principle and floatation applications of floatation principle of floatation and its applications when do objects float on water?

  1. more than the density of ice

  2. less than the density of ice

  3. same as the density of ice

  4. none of the above

Show answer
Correct Option: A
Explanation:

Given, That the ice cube is floating in the liquid.

Let the height of ice cube be $h,$
Given, If ice cube completely melts, the level of liquid raises. So initially the length of ice cube submerged in liquid be $l <h,$
Let the density of liquid be $d _{l}$ and density of ice cube be $d _{i}$
In equilibrium , $Mg=M _{l}g$
$\Rightarrow d _{i}Ahg=d _{l}Alg$
$\Rightarrow \frac{d _{l}}{d _{i}}=\frac{h}{l}>1$
$\Rightarrow d _{l} > d _{i}$
Therefore the density of liquid is more than the density of ice.
So option $A$ is correct.

An ice cube contains a large air bubble. The cube is floating on the surface of water contained on a trough. What will happen to the water level, when the cube melts?

physics upthrust in fluids, archimedes' principle and floatation applications of floatation principle of floatation and its applications when do objects float on water?

  1. $It\ will\ remain\ unchanged$

  2. $It\ will\ fall$

  3. $It\ will\ rise$

  4. $First\ it\ will\ and\ then\ rise$

Show answer
Correct Option: B
Explanation:

Since density of a hollow ice cube is less than water. Hence it will float and when ice melts, then level of water decreases due to loss in volume.

A mercury drop of water has potential 'V' on its surface. $1000$ such drops combine to form a new drop. Find the potential on the surface of the new drop.

physics energy : forms and sources renewable and non-renewable resources renewable and non-renewable sources of energy production of electricity from solar energy

  1. V

  2. $10$V

  3. $100$V

  4. $1000$V

Show answer
Correct Option: C
Explanation:

Potential of single smaller Hg drop of water =$\dfrac{Kq}{r}$=V-----(1)

and we know potential of n smaller Hg drop of water $=\dfrac{Knq}{R}$------(2)
Volume of 1000 small drops = volume of larger drop
$1000\dfrac{4}{3}\pi {r}^{3}=\dfrac{4}{3}\pi {R}^{3}$
Thus radius of bigger droplet $R=10r$
 Now putting the value of R in equation 2 we get
Potential of larger drop$=\dfrac{1000Kq}{10r}$=$100V$  

There will be an increase in potential energy of the system if work is done upon the system by

physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy production of electricity from solar energy

  1. any conservative or non-conservative forces

  2. a non-conservative force

  3. conservative force

  4. None of the these

Show answer
Correct Option: C
Explanation:

Since potential energy defined only for conservative force. It will increase for conservative force.

Potential energy of a body depends on its:

physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy production of electricity from solar energy

  1. motion

  2. colour

  3. mass

  4. none of these

Show answer
Correct Option: C
Explanation:

We know that potential energy is the energy possesd by the virtue of its position.
So, $F = mgh $
Where, $ m = $ mass
So, From above equation we can deduce that potential energy depends on the mass of the substance.

Energy possessed by a body by virtue of its position at a height is :

physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy production of electricity from solar energy

  1. Kinetic energy

  2. Chemical energy

  3. Potential energy

  4. Magnetic energy

Show answer
Correct Option: C
Explanation:

Potential energy of a body is defined as energy possessed by a body by  virtue of its position at a height.
$ P.E = mgh$

A particle of mass m travels with a speed v along positive direction of x-axis parallel to the line y=4. At t=0, the particle is at (0,4),. The angular momentum of the particle about the origin is 

physics rotational motion of a rigid body and moment of inertia angular momentum (l) and conservation of angular momentum angular momentum in case of rotation about a fixed axis law of conservation of angular momentum

  1. 0

  2. 4 mv directed along the positive z- axis

  3. 4 mv directed along the negative z- axis

  4. 4 mv directed along the positive y- axis

Show answer
Correct Option: C
Explanation:
The correct option is C

We have,

$Mass=m,Speed=v$

A particle is moving along a straight line parallel to the y-axis.

So, position vector $(\hat r ) = 4 \hat j$ 

velocity of body $\hat V = v \hat i$

Since we know,

Angular momentum = $m(\hat r \times\hat V)$

$=m ( 4 \hat j \times v \hat i)$

$=-4mv\hat k$

Since,

$I \times j = k$ 
And, $j \times i = - k$

A spinning ice skater can increase his rate of rotation by bringing is arms and free leg closer to his body.
How does this procedure affect the skater's angular momentum and kinetic energy?

physics rotational motion of a rigid body and moment of inertia angular momentum (l) and conservation of angular momentum angular momentum in case of rotation about a fixed axis law of conservation of angular momentum

  1. Angular momentum remains the same while kinetic energy increases

  2. Angular momentum remains the same while kinetic energy decreases

  3. Both angular momentum and kinetic energy remain the same

  4. Angular momentum increases while kinetic energy remains the same

Show answer
Correct Option: C

The angular momentum of a moving body remains constant if

physics rotational motion of a rigid body and moment of inertia angular momentum (l) and conservation of angular momentum angular momentum in case of rotation about a fixed axis law of conservation of angular momentum

  1. net external force is applied

  2. net pressure is applied

  3. net external torque is applied

  4. net external torque is not appled

Show answer
Correct Option: D

Which of the following laws is not always true as per the present world?

physics rotational motion of a rigid body and moment of inertia angular momentum (l) and conservation of angular momentum angular momentum in case of rotation about a fixed axis law of conservation of angular momentum

  1. Law of conservation of Angular momentum

  2. Law of conservation of Charge 

  3. Law of conservation of linear momentum

  4. Law of conservation of Energy 

Show answer
Correct Option: C