Physics problems

Correct Answer: Nuclear fission

Correct Answer: 30000 deg Cent

Explanation:

Lightning is extremely hot ? a flash can heat the air around it to temperatures five times hotter than the sun?s surface. This heat causes surrounding air to rapidly expand and vibrate, which creates the pealing thunder we hear a short time after seeing a lightning flash.

Lightning heats the surrounding air to about 30,000 degrees Centigrades.

Correct Answer: capillary action phenomenon

Explanation:

The absorption of ink by blotting paper involves capillary action phenomenon because the blotting paper is a thin and a smooth paper which allows a little thicker liquids like ink to absorb.

Correct Answer: 30 m/s

Explanation:

The interval between object pass the same point is 4 sec.

That means in 2 sec, object reaches the top and in next 2 sec, it again reaches the same point.

By the info given, we can find the velocity of that point by using : v=u+(-gt)

0= u - 10×2

u = 20

Then the velocity at 25m is 20m/sec.

so the initial velocity is

$$\begin{gathered} - v 2 = u 2 + ( - 2 gh ) \\ 400 = u 2 - 2 x 10 x 25 \\ u 2 = 900 \\ = > u = 30 m / s \end{gathered}$$

Correct Answer: higher frequency

Explanation:

As the frequency of sound is higher, women have shriller voices than men.

The shrillness or pitch of a sound is determined by its frequency. The higher the pitch shriller the voice. As the sounds produced by vocal cords of women are higher than men so women have shriller voices than men. Because their vocal cord is of smaller size. As their vocal cord is more stretched than men's.

Correct Answer: There are approximately 6 trillion miles in a light-year, so the distance we need to go is 6 trillion miles / light-year times 4 light-years is equal to 24 trillion miles So, this whole would take 12 billion hours There are 24 hours a day and 36525 days per year, so this time in years is 137 thousand years

Correct Answer: TRUE

Explanation:

True, Air is a Mixture.

Air is considered as mixture for the following reasons ;

1. Air can be separated into its components like N2, O2 , Argon and CO2 by the process of fractional distillation of liquid air.

2. Air shows the properties of all the gases present in the atmosphere.
For example : Oxygen is good Supporter of combustion. Hence air also is good supporter of combustion.

3. Air does not have a fixed formula.

4. Air has a variable composition because air at different places contains different amount of gases.

5. Heat or Light energy is neither absorbed nor released when air is prepared physical by mixing required amount of gases .

6. Mixture does have fixed boiling Point. It holds good in case of liquid air.

Correct Answer: D

Explanation:

To complete the vertical loop, the minimum speed required at the lowest point  = 5 g R.

Correct Answer: All the above

Explanation:

Processes that require or give off heat will be limited to changes of state, known as phase changes, and changes in chemical constitution, or chemical reactions. Changes of state involve a solid melting, a liquid freezing, a liquid boiling or a gas condensing.

 

An exothermic process is one that gives off heat, which is transferred to the surroundings. An endothermic process is a reaction which heat has to be supplied to the system from the surroundings.

 

Here in all the given options, heat is taken away from them to change there phase. 

Liquid to Solid --- Freezing

Gas to Liquid --- Condensation

Gas to Solid --- Deposition 

are all examples of exothermic processes.

 

Correct Answer: Pyranometer

Explanation:

Solar radiation instruments may be produced to measure different types of solar energy. When sunlight encounters the Earth's atmosphere, some of it is absorbed or scattered by water vapor, aerosols, clouds, and other air molecules. The radiation which penetrates to the Earth's surface is termed direct solar radiation.

 

A thermopile pyranometer is a type of actinometer used for measuring solar radiation on a planar surface and it is designed to measure the solar radiation flux density (W/m2) from the hemisphere above within a wavelength range 0.3 ?m to 3 ?m.