Unit of Speed - Definition, Formula, FAQs
Speed is the measure of how fast an object moves. It is defined as the rate of change of distance with time. Speed tells us how much distance an object covers in a certain time. The SI unit of speed is metre per second (m/s), but in daily life, we often use kilometres per hour (km/h) or, in countries like the US and UK, miles per hour (mph). Speed, time, and distance are related, and if we know any two, we can calculate the third using the formula: Speed = Distance ÷ Time. This topic is very important for exams appearing in problems about trains, boats, races, clocks, or moving objects, and is also common in competitive exams.
This Story also Contains
- What is Speed and its SI unit?
- Units of Speed
- Conversion of Speed, Time, and Distance
- Real-Life Applications of Speed
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What is Speed and its SI unit?
Speed
Definition: Speed is the measure of how fast an object is moving. It tells us the distance travelled by an object in a unit of time.
Formula:
$\text { Speed }=\frac{\text { Distance }}{\text { Time }}$
Units of Speed
Speed is measured as distance traveled per unit time.
SI Unit: Metre per second (m/s)
Units of Speed in Different Systems
Speed is measured as distance traveled per unit time. Its units differ in various systems of measurement:
| System | Unit of Speed | Symbol |
| CGS (Centimetre-Gram-Second) | centimetre per second | cm/s |
| MKS (Metre-Kilogram-Second) | metre per second | m/s |
| FPS (Foot-Pound-Second / Imperial) | foot per second | ft/s |
Conversion of Speed, Time, and Distance
Speed:
- $\mathrm{km} / \mathrm{h} \rightarrow \mathrm{m} / \mathrm{s}$ : multiply by $5 / 18$
- $\mathrm{m} / \mathrm{s} \rightarrow \mathrm{km} / \mathrm{h}$ : multiply by $\mathbf{1 8} / \mathbf{5}=\mathbf{3 . 6}$
Distance:
- $1 \mathrm{~km}=1000 \mathrm{~m}$
- 1 mile $=1.609 \mathrm{~km}=5280 \mathrm{ft}=1760 \mathrm{yd}$
- $1 \mathrm{yd}=3 \mathrm{ft}$
Time:
- 1 hour $=60 \mathrm{~min}=3600 \mathrm{~s}$
Real-Life Applications of Speed
- Travel and Transportation: Speed helps in calculating travel time for cars, trains, and flights.
- Sports: Athletes’ performance is measured by speed, like running, cycling, or swimming.
- Traffic Management: Speed limits ensure road safety and control traffic flow.
- Air and Space Travel: Speed is crucial for airplanes, rockets, and satellites to reach destinations on time.
- Emergency Services: Ambulances, fire trucks, and police vehicles rely on high speed to respond quickly.
- Engineering and Machines: Machines and conveyor belts are designed based on operational speed for efficiency.
Also check-
- NCERT Exemplar Class 11th Physics Solutions
- NCERT Exemplar Class 12th Physics Solutions
- NCERT Exemplar Solutions for All Subjects
NCERT Physics Notes:
Related Topics Link,
- Difference Between Distance and Displacement
- Unit of Distance
- Difference Between Speed and Velocity
- Distance and Displacement
- Measurement of Speed
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Frequently Asked Questions (FAQs)
There are three types of speed:
- Uniform Speed: Equal distance in equal time (e.g., car at constant 60 km/h).
- Non-Uniform Speed: Unequal distance in equal time (e.g., car in city traffic).
- Average Speed: Total distance ÷ Total time (e.g., 150 km in 3 hours → 50 km/h).
Unit speed is the speed at which an object travels 1 unit of distance in 1 unit of time. It represents the standard measure of speed in a system of units.
Other units of speed include kilometres per hour, meters per second, feet per second, miles per hour,, rpm, and knots, to name a few.
An SI unit is required to distinguish each measurement from the rest. A basic numerical phrase, which may mean a thousand things, is confusing and unclear. You will therefore require a fundamental speed unit to distinguish it from other metrics.
Now, if you ask what is the basic speed unit is, the response is –
The SI speed unit is a meter per second. This speed unit indicates how many meters an object may travel in a second. Say, 10 meters a second a body travels. The body speed is 10 meters per second in this example.
The SI speed unit is entered in m/s.
The centimetre per second (cm/s) or centimetres per second (cm s-1) is the CGS unit of speed.
Speed is the distance travelled by a body in a certain amount of time. Its SI unit is m/s. Speed is the distance travelled by a body in a certain amount of time. Km/s is its SI unit.