Physics ch1 important SQ

Question 1

Several repetitive phenomenon occurring in nature, also serves as a reasonable time standard.

Answer 1

the phenomenon that repeats itself after some interval is known as repetitive phenomenon which can be served as reasonable time standard

1. day and night
2. sunset and sunrise
3. lattice vibrations in crystals

Question 2

drawbacks to use period of pendulum as time standard

Answer 2

T=2π√ℓ/g
this time period can not be served as standard due to several reasons:

1. time period of simple pendulum may varies with g and g varies with altitude.
2. the length of pendulum may change with temperature

Question 3

why do we find it useful to have two units for the amount of substance kilogram and mole?

Answer 3

when we are concerned with the number of particles then we use mole as a unit amount substance. 1 mole = Na =6.02x10 (23)

when concerned about quantity of matter we use unit Kilogram

Question 4

Define possible errors in stopwatch

Answer 4

2 types
systematic error
stopwatch may be faulty

and random error
negligence and inexperience of person
at the time when stop watch starts or stops

Question 5

write 2 uses of dimensions

Answer 5

1. checking the homogeneity of physical equation.

2. driving the possible formula

Question 6

dimension of pressure

Answer 6

[Pressure] = [P] = [F] = [ma] = [M][LT-2]/L2] = [ML1-T-2]

[A] [A]

Question 7

dimension of density

Answer 7

[Density] = [m]/[V] = [M]/[L3] = [ML3]