Which phase change is an example of an exothermic process?

Correct Answer: D

Explanation:

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

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: 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: 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: 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: 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.

Correct Answer: P1V1 = P2V2

Explanation:

Ideal Gas Law ::

The Combined gas law or General Gas Equation is obtained by combining Boyle's Law, Charles' Law, and Gay-Lussac's Law. It shows the relationship between the pressure, volume, and temperature for a fixed mass (quantity) of gas:

P 1 V 1 T 1 = P 2 V 2 T 2

 

Hence, the Boyle's law P1V1 = P2T2, relates to ideal gas equation.

Correct Answer: Hydrogen

Explanation:

Entropy is a measure of disorder . It will be maximum in gases followed by liquids and least in solids.

 

Hence, here the gas is only hydrogen and it has the highest entropy.

Correct Answer: molecules of the dispersion medium colliding with dispersed phase particles

Explanation:

When their is a colloid in the solution, then it will show the Brownian movement, such as dust particle in the air will show the Brownian movement.

 

Hence, Brownian movement arises due to the impact of the molecules of the dispersion medium with the colloidal particles. It has been postulated that the impact of the molecules of dispersion medium on the colloidal particles are unequal.

 

This leads to the zig-zag (random) motion of the colloidal particles.

Correct Answer: 100000 ohm

Explanation:

Under dry conditions, the resistance offered by the human body may be as high as 100,000(10^5) Ohms.

 

Depending on the person, a rough value for the internal resistance of the human body is 300-1,000 Ohms. The skin's resistance is much lower if it is wet or burnt/blistered.



There are a lot of factors involved and not every person has the same electrical resistance. For instance, men tend to have lower resistance than women.

Within the body, the tissues with the greatest resistance are bone and fat - nerves and muscle have the least resistance.