- What do you do when you are playing a game and you should not let your friend catch you?
- What do you do when you did not catch the ball and it is going away from you?
- What do you do when a dog is running behind you?
In all the above activities you only did one thing. what is it?
Yes, you were RUNNING.
Why do you run?
When you can walk and go to someplace, why do you run?
Yes, by running you can go FAST.
Now, what do you mean by “FAST”?
How do you tell something is moving fast?
The answer to all these questions is “SPEED“.
Speed & Velocity
Speed is how fast something is moving.
- The cars on the road move very fast, they have more speed.
- A tortoise moves slowly, it has less speed.
- You are coming home from school, how do you come? Yes, you start running! You are moving with more speed.
How do you know if something is moving FAST?
We say something is fast when it travels more distance in less time.
- If something is moving with less speed then they travel less distance in more time.
- If something is moving with more speed then it will travel more distance in less time.
You and your friend are running towards your school. but you reach school first. The distance was the same for both of you but you came to school first. Why?
Because you were running faster, with more speed. your friend was running slow, with less speed.
Story Time: A Day in the Forest
Akash was watching tv one day. He saw a program on discovery channel called “a day in the forest“. The program was showing different animals, insects, birds that live in the forest.
He saw a red insect with blue wings which were flying, it landed on a very big yellow colored flower. It moved slowly into the flower.
This was a chameleon that was changing its colors. Sometimes it was blue. Sometimes purple, and then it changed to brown. It was moving very slowly on a tree branch.
There was a monkey which was jumping from one tree to another. it was eating the fruits on the tree. when there were no more fruits on trees then the monkey jumped on another tree.
Then they showed a lion. The lion was big and hungry. Lion saw a deer far away. The lion went near the deer slowly. Then the deer saw that lion is coming and it started to run. The lion was running slow. the deer was running fast. They lion then caught the deer even though the deer was moving faster.
- Think of different animals and write down which animal moves with more speed and which animal moves with less speed.
- Even though the lion and deer were running at the same speeds. how did the lion catch the deer?
In the above example, you can see two ways to go to your home, one is red and another is blue. In which way will you reach home faster from your school. red or blue?
You will reach faster on the blue way because in the red way you have to turn so many times and in the blue way you go straight to your home.
Why do you think you go reach faster in the blue path?
Velocity is when you move only in one direction.
Velocity = Speed + Direction
When we measure the speed of an object in only one direction we get the velocity of the object.
In the lion and deer story in lion caught the deer because it was running towards the deer only. the deer was not running in one direction. this means the speed of the lion and deer were the same but the velocity of the lion was more that is why it caught the deer.
In the school and home example, you reached home faster because you were travelling in only one direction.
Formula and Exercise
let us learn how to measure the speed of different objects. if an object is moving fast or moving slow, then the speed with which it is traveling can be calculated. we only need two things when measuring speed.
Distance: it is the distance between the starting point and ending point.
The distance between your home and the sweet shop is 1000 meters. the distance between your home and your friend’s home is 2000 meters.
Time: it is the time taken by someone to move from the starting point to the ending point.
If you walk to the sweet shop from your home then it takes you 40 minutes to go to a sweet shop
It takes you 15 minutes to go from your house to your friend’s house
How to measure speed?
Speed is the distance between the starting and ending point divided by the time taken to go from the starting point to the ending point.
If the distance between your home to school is 1000 meter and you go to school in 15 minutes then your speed is
Speed= distance ÷ time
Distance is 1000 meter and time is 15 minutes
Speed = 1000÷15
- The distance between Latha’s house and Manish’s house is 400 meters and Latha goes to Manish’s house in 5 minutes. with what speed is Latha moving?
- A monkey jumps from a banyan tree to a neem tree in 1 minute. the distance between the trees is 100 meters. with what speed did the monkey jump?
- Karthik and Deepak were playing cricket and Karthik hit the ball very far away. Deepak started to run and catch the ball in 3 minutes. if the distance between the ball and Deepak is 600 meters. what was the speed of Karthik?
1 ) What does the speed of an object tell us?
- It tells us about how fast the object is moving
- It tells us the name of the object
- It tells us nothing about the object
- It tells us how far away is the object from us
2 ) How is the speed of a bike or car measured?
- Speed is measured by using a measuring tape
- Speed cannot be measured
- Speed is measured by a speedometer
- Speed does not exist
3 ) The formula of speed is, speed = ______
- Distance * time
- Distance / time
4 ) Speed has direction and velocity does not have a direction ( )
5 ) If Ramu travels 100 meters in 20 seconds what is his speed?
6 ) If the speed of an object is in only one direction then the object has _____?