Solutions of physics online class test 2 of class 9

 1.As per Vikram calendar 1 year is equal to

Ans. 1 year =354.37 days.

Hindu calendar as well as Muslim calendars are based on the  phases of moon (revolution of moon around the earth) . Whereas Gregorian calendar or Western calendar is based revolution of earth around the sun.

2.Which one is incorrect & why

Ans.W- watt,N- newton,s- second,M does not represent any unit. m- metre.

So,M is incorrect. The correct option is (D).

3.Which is not the unit of time

Ans. Light year=9.46 × 10¹⁵ m  & parallactic second= 3.08 × 10¹⁶ m , both are units of distance.

So, the correct option is (C).

4.Establish a relationship between smallest & biggest unit of mass

Ans. Biggest unit(solar mass)=2×10³⁰ kg

Smallest unit(atomic mass unit)= 1.66×10-²⁷ kg

1a.m.u = 1.66 × 10-²⁷×1 kg

1 a.m.u / 1.66 × 10-²⁷ = 1kg

(1/1.66 ) × 10²⁷ a.m.u = 1kg

0.6024 × 10²⁷ a.m.u = 1 kg

1 solar mass = 2× 10³⁰ kg

                        = 2× 10³⁰ × 1 kg

                        = 2× 10³⁰ × 0.6024 × 10²⁷ a.m.u

                        =1.2048 × 10³⁰+²⁷ a.m.u

                        = 1.2047 × 10⁵⁷ a.m.u

So, the correct option is (A).

5.A pendulum takes 0.45 s for a pendulum bob to move from one mean position to one end.The length of a pendulum is 

Ans.Pendulum takes 0.45 seconds for a pendulum Bob to move from mean position to one end.

Time period= 4 × time taken to move from mean position to extreme position.

T = 4× 0.45 s

   = 1.80 s

But ,T= 2π√(l/g)

T²= 4 π² l/g

T²g / 4π² = l

(1.80 s × 1.80 s × 9.8 ms-² ) /4×(3.14)² = l

31.752 m / 39.4384 = l

0.8051 m = l

0.81 m = l

So, the correct option is (C) .

6.Compare the lengths of two simple pendulums of time periods of 2 s & 9 s.

Ans.T₁= 2s

T₂= 9 s

l₁= ?

l₂= ?

T= 2π√(l/g)

T₁=2π√(l₁/g)

T₂= 2π √(l₂ / g)

T₁/ T₂ =2π√(l₁/g) / 2π √(l₂ / g)

T₁/ T₂ = √(l₁/l₂)

  squaring both sides ,

(T₁/ T₂ )² = l₁/l₂

(1s/9s)² =l₁/l₂ (putting the values of T₁& T₂ )

1/81 =l₁/l₂

7.A seconds pendulum is taken from Leh to Kolkatta

Ans. Time period decreases.because time period is inversely proportional to square root of  acceleration due to gravity.

Acceleration due to gravity decreases with height above the earth surface.

Leh is at higher height where as Kolkata is at almost sea level.

8.1 Shake is equal to

Ans.1 shake =10-⁸ s

1shake = 10-⁸ × 10-¹ × 10¹ s

              = 10-⁸-¹ × 10¹ s

              = 10-⁹ ×1s× 10 

              = 10×10-⁹s 

             = 10× 1ns.  (10-⁹ s = 1ns)

             = 10ns

So, the correct option is (C).

9.India adopted metric system of units in 

Ans.1956

10.The National physical laboratory is situated at

Ans.New Delhi

11. The average distance between the Earth & the Sun is called

Ans.Astronomical unit

12.To avoid powers of 10 in the magnitude of a quantity ............ can be used with its unit.

Ans.prefix

13.The mass of a molecule of hydrogen is 3.332kg.The mass of 5 kg mol of hydrogen gas

Ans. Mass of a molecule of hydrogen= 3.332 × 10-²⁷ kg.

1 kg mole of hydrogen gas will contain 6.02 × 10²⁶ molecules of hydrogen.

The mass of 5 kg mole of hydrogen gas= 5× 1 kg mole of hydrogen gas.

= 5× (6.02 × 10²⁶ ) × 3.332 × 10-²⁷ kg

= 5×6.02×3.332×10²⁶-²⁷ kg

= 30.10× 3.332× 10-¹ kg

= 100.2932 × 10-¹ kg

= 10.0932 × 10¹ ×10-¹ kg

= 10 × 10¹-¹ kg

  = 10 × 10⁰ kg

 = 10 × 1 kg

= 10 kg.

So, the correct option is (C).

14.Which one is odd & why

Ans. Power is odd because it is a scalar quantity..

15.Which one is not essential for the unit to be accepted internationally

Ans.The unit should be of convenient size.

16.The year 900 had February of ...... days.2

Ans.28 days.

17.In which year two basic units were defined

Ans.1889.

18.A unit in its short form is never written in ..........   .

Ans.plural.