Unit of Distance Overview
What is the Unit of Distance? Around us, there are many objects to measure. It can be as small as an atom and as large as the cosmos or a planet in terms of size and form. However, there are various units used for different objects if we need to determine the distance between two objects, whether they are tiny or big. A separate unit is used to measure the distance between two atoms, and a different unit is used to measure the size of massive worlds.
What is Distance?
Distance is a scalar quantity that refers to the total length of the path covered by an object during its motion. It is a measure of the separation between two points, or the total amount of ground covered by an object during its motion, irrespective of the direction of the motion.
Distance is typically measured in units such as meters (m), kilometers (km), miles (mi), and feet (ft).
Distance Measurement
The units we can use to measure distance include centimeters, meters, and kilometers. A measure in the CGS system is a centimeter/ cm.
SI Unit of Distance
The SI unit of distance is the meter (m). The meter is defined as the length of the path traveled by light in a vacuum during a time interval of 1/299,792,458 of a second. The meter is the base unit of length in the International System of Units (SI) and is used to measure distances ranging from subatomic particles to astronomical distances.
We can use a meter as a base unit in association with some equations to determine other units of various physical variables such as volume, area, acceleration, and speed.
Metric Unit of Distance
The metric unit of distance is also the meter (m), which is the base unit of length in the International System of Units (SI). The meter is used to measure distances ranging from very small distances, such as the size of atoms and molecules, to very large distances, such as the distance between planets and stars.
The table below shows metric units of Distance:
|
Unit |
Symbol |
|
Millimeter |
mm |
|
Centimeter |
cm |
|
Meter |
m |
|
Kilometer |
km |
- CGS and MKS units of the system form the metric units of distance.
- CGS system = centimeter, gram, seconds
- MKS system = meter, kilogram, seconds
Unit of Distance Conversion
The table below shows the different conversions of Distance:
|
Units → ↓ |
Millimeter(mm) |
Centimeter(cm) |
Meter(m) |
Kilometers(km) |
|
1 Millimeter(mm) |
1 |
0.1 |
0.001 |
0.000001 |
|
1 Centimeter(cm) |
10 |
1 |
0.01 |
0.00001 |
|
1 Decimeter(m) |
100 |
10 |
0.1 |
0.0001 |
|
1 Meter(m) |
1,000 |
100 |
1 |
0.001 |
|
1 Kilometer(km) |
1,000,000 |
100,000 |
1000 |
1 |
|
1 inch(in) |
25.4 |
2.54 |
0.0254 |
0.0000254 |
Read more about the Orbital Velocity Formula.
Measurement of Large Distances
Metre measures are only helpful in measuring short lengths. A meter scale, however, cannot be used to determine vast lengths such as planet-to-planet or planet-to-star distances. To quantify it, we need a bigger scale. We use measures such as light year, parsec, and celestial units to measure long distances.
The Celestial Unit denotes the average distance between the Earth and the Sun. The average distance between the Earth and the Sun is approximately 1.496 1013 cm, or 93 million miles. A light year is another measurement for measuring distance.
The distance traveled by light in a year is measured in light - years from earth. 1 light year equals 9.46 1017 cm.
The mean radius of Earth's orbit that subtends an angle of one second of arc is measured in parsecs (pc). It is an astronomical distance measure. The parsec unit of measurement is used to calculate distances to stars and galaxies.
1 parsec equals 3.26 light years = 296,265 Astronomical Units
Here are some methods that are commonly used to measure large distances:
- Parallax:Parallax is a method used to measure the distance to nearby stars. It involves observing the star from two different points in Earth's orbit around the Sun and measuring the shift in the star's apparent position. This shift is called the parallax angle and can be used to calculate the distance to the star.
- Radar Ranging:Radar ranging is a technique used to measure the distance to objects in the solar system, such as planets, moons, and asteroids. It involves sending a radar signal to the object and measuring the time it takes for the signal to bounce back. This time can be used to calculate the distance to the object.
- Spectroscopic Parallax:Spectroscopic parallax is a method used to measure the distance to stars that are too far away for the parallax method. It involves measuring the star's spectrum and using it to determine its luminosity. By comparing the star's luminosity to its apparent brightness, the distance to the star can be calculated.
- Cepheid Variables: Cepheid variables are stars that pulsate in a regular pattern. The period of the pulsation is related to the star's luminosity, which can be used to calculate its distance. This method is often used to measure distances to galaxies and other objects beyond our own galaxy.
- Cosmological Redshift:Cosmological redshift is a phenomenon where light from distant galaxies is shifted to longer wavelengths due to the expansion of the universe. By measuring the amount of redshift, astronomers can calculate the distance to the galaxy.
These are just a few examples of the methods used to measure large distances in astronomy. Each method has its strengths and limitations and is used in different situations depending on the distance and the precision required.
Other Measuring Unit of Distance
- 10 meters = 1 decameter
- 10 decameters = 1 hectometer(hm)
- 10 decameters = 100 meters
- 10 hectometers = 1 kilometer
- 10 hectometers = 1000 meters
Read More About:
Unit of Distance: Things to Remember
- The standard unit of distance in the International System of Units (SI) is the meter (m).
- Distance can be measured in different units, including metric units such as millimeters, centimeters, kilometers, as well as imperial units such as inches, feet, yards, and miles.
- It's important to use the appropriate unit of distance for the task at hand and to convert between units as needed.
- Distance is a scalar quantity, meaning it has magnitude but no direction.
- The distance travelled by an object is the total length of its path from its starting point to its ending point.
- The displacement of an object is the change in its position and takes into account its starting and ending points as well as its direction of travel.
- Distance and displacement are not always the same, and an object can travel a certain distance but have zero displacements if it ends up back where it started.
- Distance can be measured using various instruments, including rulers, tape measures, odometers, and GPS devices.
Read more about the Difference Between Distance and Displacement.
Unit of Distance: Sample Questions
Convert 250 cm to meters.
Solution:To convert cm to meters, we divide by 100, so 250 cm = 2.5 meters.
A car travels at a speed of 60 km/h for 2 hours. What is the distance travelled by car?
Solution:To find the distance travelled, we use the formula: distance = speed x time. Plugging in the values, we get: distance = 60 km/h x 2 h = 120 km.
A person walks 500 meters in 5 minutes. What is the person's speed in meters per second?
Solution:To find the speed in m/s, we need to convert the time to seconds and then use the formula: speed = distance/time. Converting 5 minutes to seconds, we get 300 seconds. Plugging in the values, we get: speed = 500 m/300 s = 1.67 m/s.
An aeroplane flies at a speed of 800 km/h. How long does it take to travel 4,000 km?
Solution:To find the time, we use the formula: time = distance/speed. Plugging in the values, we get: time = 4,000 km/800 km/h = 5 hours.
The radius of a circle is 10 meters. What is the circumference of the circle?
Solution:The formula for the circumference of a circle is: circumference = 2 x pi x radius. Plugging in the values, we get: circumference = 2 x 3.14 x 10 m = 62.8 meters. Therefore, the circumference of the circle is 62.8 meters.
What is the distance between two points if their coordinates are (3,4) and (6,8) on a graph where each unit represents one meter?
Solution: The distance between the two points can be calculated using the distance formula: d = sqrt((x2-x1)^2 + (y2-y1)^2), where (x1,y1) = (3,4) and (x2,y2) = (6,8). Plugging in the values, we get: d = sqrt ((6-3) ^2 + (8-4) ^2) = sqrt (9 + 16) = sqrt (25) = 5 meters. Therefore, the distance between the two points is 5 meters.