Tag: dynamics - explaining motion

Questions Related to dynamics - explaining motion

If 1 g cm$^{-3} = 10^3\,kg\, m^{-3}$ then $10^6kgm^{-3}=$

physics dynamics - explaining motion system of unit summary of si units system of units

  1. $10^{-3}\,g\,cm^{-3}$

  2. $10^{6}\,g\,cm^{-3}$

  3. $10^{3}\,g\,cm^{-3}$

  4. $10^{-6}\,g\,cm^{-3}$

Show answer
Correct Option: C
Explanation:

Given, $1 g cm^{-3}=10^3 kgm^{-3}$

If we multiply $10^3$ on both sides, $10^3 g cm^{-3}=10^3\times 10^3 kgm^{-3}$
or $10^3 g cm^{-3}=10^6 kgm^{-3}$
Thus, option C will be the right option. 

$1^o A$ is ____

physics dynamics - explaining motion system of unit summary of si units system of units

  1. $10 nm$

  2. $0.1 nm$

  3. $100 nm$

  4. $1 nm$

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Correct Option: B
Explanation:

$1 ^oA=10^{-10} m=10^{-1}\times 10^{-9} m=0.1 nm$   (as $1 nm=10^{-9}m$)

Which among the following is the smallest prefix?

physics dynamics - explaining motion system of unit summary of si units system of units

  1. milli

  2. nano

  3. fermi

  4. deci

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Correct Option: C
Explanation:

Here, $1$ milimeter $=10^{-3}$ meter ;

$1$ angstrom $=10^{-10}$ meter ;
$1$ fermi $=10^{-15}$ meter, 

Therefore, the smallest prefix is for fermi.

Temperature can be expressed as a derived quantity in terms of :

physics dynamics - explaining motion system of unit summary of si units system of units

  1. length and mass

  2. mass and time

  3. length, mass and time

  4. none of these

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Correct Option: D
Explanation:

Temperature cannot be expressed in the terms of mass, length and time. Temperature is expressed in kelvin.

The physical quantity having the same unit in all the systems of unit is :

physics dynamics - explaining motion system of unit summary of si units system of units

  1. length

  2. mass

  3. time

  4. foot

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Correct Option: C
Explanation:

Time has same unit, second, in the SI, FPS, CGS and  MKS system. Rest of the quantities have different units in  SI, FPS, CGS and MKS system.

A ______ is the interval from one noon to the next noon.

physics dynamics - explaining motion system of unit summary of si units system of units

  1. mean solar day

  2. solar day

  3. lunar day

  4. day

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Correct Option: B
Explanation:

A solar day is the interval from one noon to the next noon.

SI unit of Magnetic flux is weber and its CGS unit is maxwell. Then 1 Wb = :

physics dynamics - explaining motion system of unit summary of si units system of units

  1. $10^6$ maxwell

  2. $10^7$ maxwell

  3. $10^8$ maxwell

  4. $10^9$ maxwell

Show answer
Correct Option: C
Explanation:

Magnetic flux is the product of magnetic field and area.

As SI unit of magnetic flux is weber, so $1 \, Wb=Tesla (T)\times m^2$
where $1 \, T=10^{4} \, gauss$ and $1 m^2=10^4 cm^2$
(T and gauss is the SI and CGS unit of magnetic field )
So, $1 \, Wb=10^4 \, gauss \times 10^4cm^2=10^8 $ maxwell

$S = A(1 - e^{-Bxt})$, where S is speed and x is displacement. The unit of B is :

physics dynamics - explaining motion system of unit summary of si units system of units

  1. $m^{-1}s^{-1}$

  2. $m^{-2}s$

  3. $s^{-2}$

  4. $s^{-1}$

Show answer
Correct Option: A
Explanation:

It is given that $x$ is displacement and $t$ is time.
Unit of $x$ is $m$ and that of time t is $s$.
Since, the quantity $Bxt$ must be dimensionless.
$\implies$ Unit of B must be $m^{-1}s^{-1}$.

Arrange the following lengths in the increasing order of their magnitudes :
1 meter, 1 centimeter, 1 kilometer, 1 millimeter .

physics dynamics - explaining motion exponentiation index notation and products of prime factors powers

  1. 1 meter < 1 centimeter < 1 kilometer < 1 millimeter

  2. 1 millimeter < 1 meter < 1 centimeter < 1 kilometer

  3. 1 millimeter < 1 centimeter < 1 meter < 1 kilometer

  4. none of these

Show answer
Correct Option: C
Explanation:

1 kilometer = 10$^3$ meter

1 centimeter = 10$^{-2}$ meter
1 millimeter = 10$^{-3}$ meter

Ascending order of length :
1 millimeter < 1 centimeter < 1meter < 1 kilometer

The wrong unit conversion among the following is

physics dynamics - explaining motion exponentiation index notation and products of prime factors powers

  1. 1 angstrom = $10^{-10} m$

  2. 1 fermi = $10^{-15}$ m

  3. 1 light year = $9.46 \times 10^{15} m$

  4. 1 astronomical unit = $1.496 \times 10^{-11} m$

Show answer
Correct Option: D
Explanation:
$A)1 $Angstrom: $1$ Ångström is equal to$ 0.1 $nanometers. Expressed in the SI base unit meters $1$ Ångström is equal to $1 \times 10^{-10}$ meters. $1 Å = 0.0000000001 m.$

$B)$Definition of fermi unit: $≡ 1\times 10^{−15} m.$

$C)$The light-year is a unit of length used to express astronomical distances and measures about $9.46$ trillion kilometres $(9.46 \times 10^{12} km)$ or $5.88$ trillion miles $(5.88 \times 10^{12} mi).$

$D)$The total radiation power received from the sun on a unit area perpendicular to the sun rays at the mean earth-sun distance, termed an astronomical unit, is called the solar constant (SC), where $1$ astronomical unit $= 1 AU = 1.496 \times 10^{11} m.$

So $D$ is wrong unit conversion