physical quantities

Question 1

physical quantities

Answer 1

a measurable quantity in terms of which the laws of physics are expressed

Question 2

unit

Answer 2

a standard chosen quantity in term of which a physical quantity is measured

Question 3

dimension

Answer 3

power to be raised on a fundamental quantities like mass(m) , length(l) ,and time (T) involved in derived physical quantity

Question 4

dimensional formula

Answer 4

the symbolic representation of dimension of physical formula in the term of m, l ,t inside larger bracket

Question 5

dimension equation

Answer 5

the dimensional formula written in the form of equation

Question 6

uses of dimensional formula

Answer 6

1. to find the dimension of constant
2. to check the correctness of the equation
3. to convert one system unit to another
4. to derive the formula

Question 7

principle of homogeneity

Answer 7

for a equation to be correct, the dimension of each term of lhs must be equal to dimension of each term on rhs

Question 8

limitation of dimensional formula

Answer 8

1. it cant be said whether a physical quantity is a scalar or a vector
2. the dimensional method cant be used to derived relations other than product of power function
3. there are many physical quantities which have the same dimensional formula
4. the relationship between more then three quantities involved in a physical phenomenon cant be derived by dimensional method

Question 9

error

Answer 9

degree of uncertainty in a measurement from real or standard value

Question 10

real error

Answer 10

real value - ovserved value

Question 11

relative error

Answer 11

real error/real value

Question 12

percentage error

Answer 12

relative error*100%

Question 13

accuracy

Answer 13

measure of the difference of the experimental value and the true value(closeness betn values)
accuracy = mean value - true value

Question 14

precision

Answer 14

difference between a measured value and the arithmetic mean value for a series of measurement(less the value more the precision)
precision = individual value - arithmetic value

Question 15

significant figure

Answer 15

the no/digits that plays significant role in a number

Question 16

notes

Answer 16

1. the dimension is only a way to write a unit of a physical quantity. quantity either constant or variable may or may not have dimension.
2. if dimensional formula is given, the physical quantity may or may not be unique .i.e. different physical quantities may have the same dimensions
3. if a quantity ha dimensional formal , it must have a unit but the converse may or may not be true
4. a quantity which is the ratio of two same quantities is dimensionless

Question 17

is dimensional correct equation necessarily physically correct?

Answer 17

no. an equation dimensional correct needs not to be physically correct but the converse must be true
s=2ut+at^2(dimensional correct but physically incorrect)

Question 18

is dimensional correct equation necessarily physically correct?

Answer 18

no. an equation dimensional correct needs not to be physically correct but the converse must be true
s=2ut+at^2(dimensional correct but physically incorrect)

Question 19

the diameter of a steel rod is given s 56.47+_0.02 mm .what does it means?

Answer 19

0.02 represents uncertainty in measurement
diameter lies betn 56.45 and 56.49 mm. thus the above measurement is unlikely to be less than 56.45 mm or greater than 56.49 mm.

Question 20

rules of significant role

Answer 20

25400(3) >without unit
25400 m(5) with unit
6540025 (7)sandwiched betn nos
0.65400025(8)in decimal
0.000645005(6)in decimal
1.00654005(9)sandwiched betn nos
2.268+2.5=2768
6.25*2.55/1.6=9.9

Question 21

to find the dimension of constant

Answer 21

a.first, put the constant in the rhs place if it is in product form
b.compare the dimension of each element and the comparison can help to find the dimension of constant
c.if it is dimensionless constant just solve the element inside it in dimensional form and find the dimension of constant
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Question 22

to check the correctness of the equation

Answer 22

a. rewrite the eqn in dimensional equation form

b. check whether the dimension of lhs = dimension of rhs

Question 23

to convert one system unit to another

Answer 23

n2=n1 [m2/m1] ^ a * [l2/l1] ^ b * [t2/t1] ^ c

where a, b, and c are the dimension, m, l and t are mass, length and time in respective system and n1 is the magnitude

Question 24

to derive the formula

Answer 24

a. depends on something and is related to it
b. combine them
c. write the dimension and solve the eqn
d. put the value in formed equation and derive the formula