Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

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

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:

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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?

  1. $It\ will\ remain\ unchanged$

  2. $It\ will\ fall$

  3. $It\ will\ rise$

  4. $First\ it\ will\ and\ then\ rise$
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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.

  1. V

  2. $10$V

  3. $100$V

  4. $1000$V
Reveal answer Fill a bubble to check yourself
C Correct answer
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$=\dfrac{1000Kq}{10r}$=$100V$  

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

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

  1. any conservative or non-conservative forces

  2. a non-conservative force

  3. conservative force

  4. None of the these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

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

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

Potential energy of a body depends on its:

  1. motion

  2. colour

  3. mass

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

Multiple choice 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

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 

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
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, $j \times i = - k$
Multiple choice 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

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?

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice 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

The angular momentum of a moving body remains constant if

  1. net external force is applied

  2. net pressure is applied

  3. net external torque is applied

  4. net external torque is not appled
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Angular momentum is conserved when the net external torque on a system is zero. Torque, not force or pressure, is what changes angular momentum. The absence of net external torque means angular momentum remains constant.

Multiple choice 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

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

  1. Law of conservation of Angular momentum

  2. Law of conservation of Charge&nbsp;

  3. Law of conservation of linear momentum

  4. Law of conservation of Energy&nbsp;
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The law of conservation of linear momentum is generally true for isolated systems, but in the presence of external forces (which are ubiquitous), it is not always conserved for a specific body. However, in the context of fundamental physics, all listed conservation laws are highly robust, but linear momentum is often cited as the one most easily 'broken' by external forces.