Question

Write the indirect methods in physics which have enabled us to know the absolute mass of almost all the known elements in this universe​

Answer 1

Answer:

One of the most remarkable simplifications in physics is that only four distinct forces account for all known phenomena. In fact, nearly all of the forces we experience directly are due to only one basic force, called the electromagnetic force. (The gravitational force is the only force we experience directly that is not electromagnetic.) This is a tremendous simplification of the myriad of apparently different forces we can list, only a few of which were discussed in the previous section. As we will see, the basic forces are all thought to act through the exchange of microscopic carrier particles, and the characteristics of the basic forces are determined by the types of particles exchanged. Action at a distance, such as the gravitational force of Earth on the Moon, is explained by the existence of a force field rather than by “physical contact.”

Answer 2

Answer:

Order of Magnitude:

Order of magnitude gives us the value nearest to the actual value, in terms of suitable powers of 10. (It does not tell us the absolute value of the quantity).

To express a number in nearest power of 10, a number less than 5 is treated as 1 and a number between 5 and 10 is treated as 10

Example: Radius of earth is 6.4 ×106 m. Taking 6.4 as 10, size of the earth is of the order of 107m.

Units and Measurement: CBSE Class 11 NCERT Solution

Measurement of length:

There are two ways to measure length or distances

(i) Direct method (ii) Indirect method

Direct Method:

• A metre scale for distances from from 10‒3 m to 102 m

• A verner calipers for distance upto 10‒4 m

• A screw gauge and a spherometer for distances upto 10‒5 m

Indirect method for measuring large distances:

Some indirect methods to measure large distances are:

Parallax method

This method is used to measure distances of planets which are very far away from earth.

When a man holds a pen in front of him against some specific point on the background (a wall) and look at the pen first through his left eye A (closing the right eye) and then look at the pen through his right eye B (closing the left eye), he would observe that the position of the pen seems to change with respect to the point on the wall. This is called parallax.

Explanation:

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