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What is km/h (Kilometres Per Hour)?
Grade Level:
Class 5
Physics, Computing, AI, Transport, Geography
Definition
What is it?
km/h stands for Kilometres Per Hour. It is a unit that tells us how fast something is moving. It shows the distance (in kilometres) an object travels in one hour.
Simple Example
Quick Example
Imagine your school bus travels from your home to school. If it covers 20 kilometres in 1 hour, we say its speed is 20 km/h. This means for every hour it drives, it covers 20 kilometres.
Worked Example
Step-by-Step
PROBLEM: A car travels 150 kilometres in 3 hours. What is its speed in km/h?
Step 1: Understand what is given. Distance = 150 km, Time = 3 hours.
---Step 2: Remember the formula for speed: Speed = Distance / Time.
---Step 3: Put the given values into the formula. Speed = 150 km / 3 hours.
---Step 4: Perform the division. 150 divided by 3 is 50.
---Step 5: Add the unit. The unit for distance is km and for time is hours, so the speed unit is km/h.
---Answer: The car's speed is 50 km/h.
Why It Matters
Understanding km/h helps us measure how fast things move, which is super important in Physics. It's used by pilots to fly planes, by app developers to show how long a delivery will take, and even in AI to control self-driving cars. This concept is key for many exciting careers!
Common Mistakes
MISTAKE: Confusing distance with speed. Students might think 100 km is a speed. | CORRECTION: 100 km is a distance. 100 km/h is a speed. Speed always has a distance unit AND a time unit.
MISTAKE: Not converting time units when needed (e.g., using minutes directly in km/h calculation). | CORRECTION: For km/h, the time must always be in hours. If given in minutes, divide by 60 to convert to hours.
MISTAKE: Dividing time by distance instead of distance by time. | CORRECTION: Always remember Speed = Distance / Time. Distance is always the numerator (top number) and Time is the denominator (bottom number).
Practice Questions
Try It Yourself
QUESTION: A train travels 300 km in 4 hours. What is its speed in km/h? | ANSWER: 75 km/h
QUESTION: An auto-rickshaw covers 45 km in 90 minutes. What is its speed in km/h? (Hint: Convert minutes to hours first) | ANSWER: 30 km/h
QUESTION: A cyclist rides at a speed of 20 km/h for 2 hours, then rests for 1 hour, and then rides another 30 km in 1 hour. What is the total distance covered and the average speed (excluding rest time)? | ANSWER: Total distance = 70 km; Average speed = 25 km/h
MCQ
Quick Quiz
What does a speed of 60 km/h mean?
The object travels 60 kilometres in 60 minutes
The object travels 60 kilometres in 1 hour
The object travels 1 kilometre in 60 hours
The object travels 60 metres in 1 hour
The Correct Answer Is:
B
60 km/h means 60 kilometres 'per' (for every) hour. Since 1 hour is 60 minutes, option B correctly states 60 kilometres in 1 hour. Option A is also correct but B is more direct.
Real World Connection
In the Real World
When you book a cab or order food on apps like Ola or Swiggy, the estimated arrival time is calculated using average speeds in km/h. Traffic updates on Google Maps also show you how fast vehicles are moving on different roads, helping you choose the quickest route based on km/h speeds.
Key Vocabulary
Key Terms
SPEED: How fast an object is moving. | DISTANCE: The total length travelled by an object. | TIME: The duration for which an event occurs. | UNIT: A standard measure used for a quantity.
What's Next
What to Learn Next
Next, you can learn about 'Metres Per Second (m/s)' and how to convert between km/h and m/s. This will help you understand speed in different situations, like for athletes in a race or smaller objects.
