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Spheres $P$ and $Q$ are uniformly constructed from the same material which is a good conductor of heat and the radius of $Q$ is thrice of radius of $P$. The rate of fall of temperature of $P$ is $x$ times that of $Q$ when both are at the same surface temperature. The value of $x$ is ;

The volume of a gas at STP is $1.12\times {10}^{-7}\text{cc}$. The number of molecules in it will be:

Why does a normal fridge has its freezer always on the top?

At which of the following locations is a compass functional?

Raju runs exactly 2 laps around a 400 metres track. Express your answer in meters. (Calculate distance and displacement).

An electric generator works on the principle of ___ induction.

Why is it necessary to wrap the current carrying conducter with an insulation to form a solinod??

A bottle weighs 20g when empty and when completely filled with water, weighs 50g and when filled with kerosene , it weighs 44g . Calculate the volume of bottle and density of kerosene oil

Pressure difference and high-speed winds are causes of __.

Why concave lens diverge and convex lens converge light rays?

An incandescent bulb works on which of the following principles:

Question 17

While travelling in a train, it appears that the trees near the track are moving whereas co-passengers appear to be stationary. Explain the reason.

What can you say about the motion of a clock's minute hand kept in a moving bus as seen from the ground?

Choose the correct one.

What is meant by "Vehicle A is moving faster than Vehicle B"? How do we find out which is faster? [2 MARKS]

Identify the part of the bulb which generates most heat in the bulb:

The relationship between Young's modulus Y, Bulk modulus K and modulus of rigidity $\eta$ is

Solution for the given system of equation is

$\frac{x+y-8}{2}$ = $\frac{x+2y-14}{8}$ = $\frac{3x+y-12}{11}$

Why is fuse wire used in electric circuits?

What makes metals good conductors of electricity?

A long wire will have:

Find the area of the shaded part in the figure given below.
(Take $\pi$ = $\frac{22}{7}$)
All the dimensions are in cm.

Which part of the object vibrates when the following sounds are produced [3 MARKS]
1. Music of a Sitar or Veena
2. Buzzing of a bee
3. Sound from a speaker

Two bodies of masses m and 4 m are moving with equal kinetic energy. The ratio of velocities with which they are traveling is :

Which speed do we take into consideration while measuring time taken to cover a particular distance?

Two cars A and B are moving with the same speed v as shown below.


With respect to car A, car B is ___.

What is the function of the filament in an electric bulb? [1 MARK]

Sushweta and Garima went to the railway station to see off Himanshu, who was going to his college. Garima told Sushweta that if she got close to the tracks when the train is passing by, she would feel a pull:

Which of these is the symbol for a series combination of cells?

What are the factors that affect the size of a shadow?

Sound is:

Which causes tropical cyclone

Which of the following is defined as the movement of heat from one place to another?

Refer to the pie charts and answer the given questions.
Q. What is the central angle corresponding to number of members in health club B?

why only we can see scattering of light only in turbid water.

According to Laws of Reflection which of the following statement is/are correct?

The time taken by a simple pendulum to complete one oscillation is known as__________.

Four cells are fixed on a board as shown below:

How will you connect the terminals with wires to make a battery of four cells?

A boy tied a string to one of the ends of a box and started sliding the box on a playground. He then observed a circular track and rushed there and completed half revolution of the track with his box. The work done by friction on the box is _____.

No medium is required for transfer of heat by

Which type of objects do not cast shadows?