Tag: motion and measurement

Questions Related to motion and measurement

In a system of units, the units of mass, length and time are called pail, jack, and jill. 1 pail = 5 kg, 1 m = 5 jacks and 24 s make 1 jill. What are the unit of density and speed in the new system?

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. $\displaystyle { (pails)\quad (jills) }^{ -2 }$

  2. $\displaystyle { (pails)\quad (jack) }^{ -3 }$

  3. $\displaystyle { (jack) }^{ 2 }(jill)$

  4. $\displaystyle { (pails)\quad (jack) }^{ 2 }$

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Correct Option: B
Explanation:

The unity of density$=\frac { unit\quad of\quad mass }{ { (unit\quad of\quad length) }^{ 3 } } \ =(pails){ (Jack) }^{ 3 }$

The value of $\displaystyle G=6.67\times { 10 }^{ -11 } N \ { m }^{ 2 } kg^{ -2 } and \ g={ 9.8ms }^{ -2 }$, what is the unit of g/G in C.G.S system?

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. $\displaystyle { g\quad cm }^{ -2 }$

  2. $\displaystyle { g\quad cm }^{ 2 }$

  3. $\displaystyle { g\quad cm }^{ -1 }$

  4. $\displaystyle { g\quad cm }$

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Correct Option: A
Explanation:
Unit of $g$ in SI is  $ms^{-1}$ and that of $G$ is $Nm^2 kg^{-2}$.
where  $1 \ N   = 1 \ kg \ ms^{-2}$ (in MKS system)

So, MKS units of $G$ is $m^3s^{-2}kg^{-1}$

Thus CGS unit of $g$ is  $cm \ s^{-2}$ and that of $G$ is $cm^3 s^{-2} g^{-1}$

Thus CGS unit of  $g/G$ is $g \ cm^{-2}$

The  SI unit of weight is.

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. kg wt

  2. N

  3. g wt

  4. all the above

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Correct Option: B
Explanation:

The weight of a body is , as the force with which the earth attracts it towards the centre.

$W= \dfrac{GMm}{R^2 }= mg$

$g$ (acceleration due to gravity) $= \dfrac{GM}{R^2}$

where,

$G$ is constant of gravitation, $R$ is distance from the centre if the earth, $M$ is the mass of the earth.

If the mass of the body $‘m'$ , the force of attraction of the earth or the $‘W'$ of the body is

$W= mg$

Weight is the force of attraction, its S.I. unit is same as that of S.I. unit of force .

The S.I. unit of weight is Newton (N).

The magnitude of a physical quantity consists of

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. a number and a unit

  2. a number

  3. a unit

  4. a unit and its symbol

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Correct Option: B
Explanation:

The magnitude of a physical quantity represent the amount contained in the quantity. Therefore, the magnitude of the quantity consists of a number only.


Option $B$ is correct.

If kg $m^2s^2$ represents 'x' and g $cm^2s^2$ represents 'y', then find the ratio of x to y.

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. 10$^7$

  2. 10$^5$

  3. 10$^9$

  4. 10$^3$

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Correct Option: A
Explanation:

We know that, 

$1 kg=1000g$
$1m=100cm$

Now, converting the unit $kg\ m^2\ s^2$ into $g\ m^2\ s^2$

$1\ kg\ m^2\ s^2=1000\ g\times(100\ m)^2\ s^2$

$=1000\times10^4\ g\ m^2\ s^2$
$=10^7 g\ cm^2\ s^2$

State whether true or false.
The measure of an angle is dependent upon the unit of length.

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. True

  2. False

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Correct Option: A
Explanation:
Plane angle is defined as the ratio of arc length to the radius.
Plane angle   $\theta = \dfrac{l}{r}$
So, the measure of an angle is dependent upon the unit of length. Thus, the given statement is true.

Which of the following unit is different from other:

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. Electron volt

  2. Kilo Watt hour

  3. Watt sec

  4. Volt

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Correct Option: D
Explanation:
Electron volt, kilo Watt hour and Watt sec are the units of energy but volt is the unit of potential difference (or voltage).
Thus volt is odd one out here.

$Weber/{m^2}$ = 

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. Tesla

  2. Dyne

  3. Watt

  4. Henry

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Correct Option: A
Explanation:
$Weber/m^2$ is the S.I. unit of magnetic field strength. Magnetic field is also measured in another SI unit $Tesla$.
$Weber/m^2 = Tesla$

1 Nanometer = ?

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. ${10^{-3}}m$

  2. ${10^{-6}}m$

  3. ${10^{-9}}m$

  4. ${10^{-12}}m$

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Correct Option: C
Explanation:
According to the standard conversions,  $1 \ nm = 10^{-9}\ m$
One nanometer is vary small unit. of distance.

Accuracy of a measurement is determined by :

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. Absolute

  2. Percentage

  3. Both

  4. None of these

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Correct Option: B
Explanation:

Percentage determines the accuracy in the measurement. More is the percentage of error, more is the error in the measurement.