Friday 18 September 2020

Solutions of physics online class test 1 of class 9

 1.Establish a relationship between British system and metric system of mass

Ans.1 lb= 453.59 g

1 lb = 453.59 × 1 g

        = 453.59 × 1/1000 kg

    1lb    = 0.45359 kg

Multiplying both sides by thousand,

1000× 1 lb = 1000× 0.45359 kg

1000 lb = 453.59 kg.

So, the the correct option is (C)

       1lb ≈0.454 kg

2.The International Bureau of Weights and Measures at Sevres is located in

Ans.paris , capital city of France.

3.Which year had february of 29 days

Ans.1600.

Those century years which are divisible by 400  are leap years.

4.Which is not a derived unit

Ans.A (ampere) is unit of current which is a fundamental quantity.

So correct option is (A).

5.kg.m.s/s² is the unit of 

Ans.kg.m.s/s²

=kgms/s.s

= kgm/s

= kg. m/s

= mass × velocity

= momentum

So, the correct option is (D).

6. 50 Angstrom is equal to

Ans. 50A°

= 50× 1A°

= 50× 10-¹⁰ m

= 5×10 × 10-⁶-⁴ m

= 5×10¹ × 10-⁴ × 10-⁹ m

= 5× 10¹-⁴ × 1μm

= 5× 10-³ μm

= 5/1000 μm

= 0.005 μm

So, the correct option is  (A).

7.1 Mean Solar day is equivalent to

Ans.1mean solar day=86400 s.

The correct option is (D).

8.The distance of a star from the earth is 8.33 light years.The distance in metre is

Ans. Distance= 8.33 light years.

= 8.33 × 1 light year

=8.33× 9.46×10¹⁵ m

=78.8018 × 10¹⁵ m

=7.88018× 10 ×10¹⁵m

=7.88018 × 10¹⁶m

The correct option is (C)

9.The frequency of a pendulum is 0.5 Hz.Then which statement is correct

Ans. Frequency= 0.5 Hz

T= 1/f

T= 1/0.5 Hz

   = 2 s

Time period of a pendulum is 2 second. It means that it is a seconds pendulum. We also know that length of a seconds pendulum is 0.99 metres.

So, the correct option is (C).

10.The size of a bacteria is 1 micron.The number of bacteria in 5.1 km length is 

Ans. Size of a bacteria= 1μm

Length=5.1 km

Number of bacteria in 5.1km length=5.1 km/size of a bacteria.

=5.1km / 1μm

= 5.1 km / 10-⁶ m

= 5.1 km × 10⁶ m-¹

= 5.1 × 10³ m ×10⁶ m-¹

=5.1 × 10³+⁶ m¹-¹

= 5.1 × 10⁹ m⁰

= 5.1 × 10⁹ × 1

= 5.1 × 10⁹

=5100000000.

So, the correct option is (A).



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