Tag: motion and measurement

Questions Related to motion and measurement

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 $S _1$

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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.

To minimise parallax error, the observer should place the object :

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

  1. as near to the scale of the ruler as possible and the eye must be directly above the scale

  2. as far to the scale of the ruler as possible and the eye must be directly above the scale

  3. as near to the scale of the ruler as possible and the eye must be to the right of the scale

  4. as near to the scale of the ruler as possible and the eye must be to the left of the scale

Show answer
Correct Option: A
Explanation:

$Answer:-$ A

There are three simple ways of reducing parallax error in that case: 
1. Attach a straight object (like a ruler or straightened paperclip) to the thing you're measuring the displacement of, it should stick out of the object perpendicularly to the scale you're measuring the displacement on. 
2. Make sure that object is as close to your scale as possible, but not touching. 
3. Put your eyes level with the object, and as close to it as you safely can.

The effect of parallax is used to measure:

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

  1. distances to nearby objects

  2. distances to nearby stars

  3. nearness of atoms in substances

  4. the object and image distance in optical experiments

Show answer
Correct Option: B
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.

A star has a parallax angle p of 0.723 arcseconds. What is the distance of the star?

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

  1. 1.38 parsecs

  2. 2.38 parsecs

  3. 3.38 parsecs

  4. 4.38 parsecs

Show answer
Correct Option: A
Explanation:

Relationship between a star's distance and its parallax angle:

$d=\dfrac{1}{p}$

The distance $d$ is measured in parsecs and the parallax angle $p$ is measured in arcseconds.

Hence, $d=\dfrac{1}{0.723}=1.38 parsecs$

Error due to eye vision is termed as :

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

  1. climax error

  2. sight error

  3. parallax error

  4. visional error

Show answer
Correct Option: C
Explanation:

$Answer:-$ C

Parallax also affects optical instruments such as rifle scopes, binoculars,microscope and twin lens reflex cameras that view objects from slightly different angles. Many animals, including humans, have two eyes with overlapping visual fields that use parallax to gain depth perception; this process is known as stereopsis.

A star's distance ($d$) and its parallax angle ($p$) are related to each other as:

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

  1. $d=\dfrac{1}{p}$

  2. $d=\dfrac{1}{p^2}$

  3. $p=\dfrac{1}{d^2}$

  4. none of these

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.

The relationship between a star's distance and its parallax angle:

$d=\dfrac{1}{p}$

The distance $d$ is measured in parsecs and the parallax angle $p$ is measured in arc seconds.

Parallax method is based on which of the following principle?

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

  1. Disparity

  2. Lutz Kelker bias

  3. Trilateration

  4. Triangulation

Show answer
Correct Option: D
Explanation:

Distance measurement by parallax is a special case of the principle of triangulation, which states that one can solve for all the sides and angles in a network of triangles if, in addition to all the angles in the network, the length of at least one side has been measured. Thus, the careful measurement of the length of one baseline can fix the scale of an entire triangulation network. In parallax, the triangle is extremely long and narrow, and by measuring both its shortest side (the motion of the observer) and the small top angle (always less than 1 arcsecond leaving the other two close to 90 degrees), the length of the long sides can be determined.