Tag: measuring length

Questions Related to measuring length

From the following, the biggest unit of energy is?

physics learning how to measure measuring length measurement of small and large distances measurement of distance unit of fundamental quantities

  1. Joule

  2. Kilowatt hour

  3. Erg

  4. Electron volt

Show answer
Correct Option: B
Explanation:

Since, we know that SI unit of energy is represented by Joule. Hence, let us convert all the different units in the form of Joules.


$1\,Joule=1\,Joule$

$1\,Kwh=3600000\,Joule$

$1\,erg=10^{-7}\,Joule$

$1\,eV=1.6\times 10^{-19}\,Joule$

Hence, Kilowatt hour is the largest unit of energy and hence it is practically used in everyday life of electric consumption.

Which one of the following methods is used to measure distance of a planet or a star from the earth?

physics motion and measurement measuring length measurement of small and large distances measurement of distance

  1. Echo method

  2. Parallax method

  3. Triangulation method

  4. None of these

Show answer
Correct Option: B
Explanation:

Astronomers estimate the distance of nearby objects in space by using a method called stellar parallax, or trigonometric parallax. Simply put, they measure a star's apparent movement against the background of more distant stars as Earth revolves around the sun

'The parallax angle in radians is: $\theta = \left( 1 + \frac { 54 } { 60 } \right) \times \frac { \pi } { 180 } = 0.03316 \mathrm { rad }$
  Hence, the distance between moon and earth: 

physics motion and measurement measuring length measurement of small and large distances measurement of distance

  1. $\dfrac { \text { Diameter of Earth } } { \theta }$

  2. $\dfrac { 1.276 \times 10 ^ { 7 } m } { 0.03316 }$

  3. $3.84 \times 10 ^ { 8 } m$

  4. nnone of these

Show answer
Correct Option: C
Explanation:

Given,

$\theta =0.03316\,\,rad$

Also $b = \mathrm { AB } =$ diameter of earth $= 1.276 \times 10 ^ { 7 } \mathrm { m }$

Now d $=\dfrac{b}{\theta }=\dfrac{1.276\times {{10}^{7}}}{0.03316\,}=3.84\times {{10}^{8}}\text{m}$

Hence, distance between earth and moon is $3.84\times {{10}^{8}}\text{m}$

Which of the following instrument can be used to determine the radius of curvature of a spherical surface?

physics motion and measurement measuring length measurement of small and large distances measurement of distance

  1. Spherometer

  2. Vernier callipers

  3. Screw gauge

  4. Simple pendulum

Show answer
Correct Option: A
Explanation:

Spherometer is an instrument which is used to measure the curvature of spherical surfaces.

Parallax method is suitable for the measurement of:

physics motion and measurement measuring length measurement of small and large distances measurement of distance

  1. ball

  2. planet

  3. vehicle

  4. distance between cities

Show answer
Correct Option: B
Explanation:

Parallax method is used for the measurement of planet distance and also used to measure distance of starts and planets

option B is correct.

Which of the following is the best method to measure microscopic distances?

physics motion and measurement measuring length measurement of small and large distances measurement of distance

  1. Optical microscope

  2. Meter scale

  3. Screw gauge

  4. Diffraction pattern

Show answer
Correct Option: A
Explanation:

Optical microscopes are enabled with objective fitted with lenses with different magnifications. This helps to magnify a small objects and so necessary measurements.

What is the approximation made in the parallax method?

physics motion and measurement measuring length measurement of small and large distances measurement of distance

  1. All distances measured between two points on earth is zero.

  2. All distances measured between two points on earth is constant.

  3. Distance between a point on the earth and the planet is very large as compared to the distance between two points on earth's surface.

  4. No approximation is made.

Show answer
Correct Option: C
Explanation:

In parallax method, an approximation is made that distance between a point on the earth and the planet is very large as compared to the distance between two points on the earth's surface.

Two stars $S _1$ and $S _2$ are located at distances $d _1$ and $d _2$ respectively. Also if $d _1>d _2$ then which of the following statements is true?

physics motion and measurement measuring length measurement of small and large distances measurement of distance

  1. The parallax of $S _1$ and $S _2$ are same.

  2. The parallax of $S _1$ is twice as that of $S _2$.

  3. The parallax of $S _1$ is greater than parallax of $S _2$

  4. The parallax of $S _2$ is greater than parallax of $S _1$

Show answer
Correct Option: D
Explanation:

$Answer:-$ D

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.Due to foreshortning, nearby objects have a larger parallax than more distant objects when observed from different positions, so parallax can be used to determine distances.

Hence parallax of $S _2$ is greater than that of $S _1$

Astronomersuse the principle of parallax to measure distances to the closer stars. Here, the term "parallax" is the semi-angle of inclination between two sight-lines to the star, as observed when the Earth is on opposite sides of the Sun in its orbit.

Parallax is the apparent displacement of an object because of:

physics motion and measurement measuring length measurement of small and large distances measurement of distance

  1. change in observer's point of view

  2. change in object's position

  3. changes both in observers point of view and object's position

  4. consistency in observer's point of view

Show answer
Correct Option: A
Explanation:

Astronomers use an effect called parallax to measure distances to nearby stars. Parallax is the apparent displacement of an object because of a change in the observer's point of view.

As the Earth orbits the sun, a nearby star will appear to move against the more distant background stars. Astronomers can measure a star's position once, and then again 6 months later and calculate the apparent change in position.

Parallax method is useful 

physics motion and measurement measuring length measurement of small and large distances measurement of distance

  1. for measuring speed of the light.

  2. for measuring distances of star.

  3. for finding the intensity of the light.

  4. None of the above.

Show answer
Correct Option: B
Explanation:

$Answer:-$ B

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. Astronomers use the principle of parallax to measure distances to the closer stars.