Question:
An athlete takes 10 second to complete a race of 200 meter. Find the speed of the athlete in kilometre per hour.
Correct Answer
72 kilometer/hour
Solution And Explanation
[Strategy to solve the Question: (1) Calculate the speed in m/s and then change this speed into kilometre per hour. (2) change the distance into km and time into hour and then calculate the speed using these units. This speed will be in the required kilometer per hour]
Given,
Distance = 200 meter
Time = 10 second
Now we know that,
Speed = Distance/Time
Thus, speed of the given athlete
= 200 meter /10 second
= 20 meter per second
⇒ Speed = 20 m/s
Conversion of speed from m/s to km/h
To convert meter per second (m/s) to kilometre per hour (km/h) we need to multiply m/s by 18 /5 .
Thus, 20 m/s
= 20 4 × 18 / 5 km/h
= 4 × 18 = 72 km/h
Thus, speed of the given athlete = 72 km/h Answer
Second method to calculate the speed in km/h using distance given in meter and time given in second.
Here, given distance = 200 meter
= 200 /1000 km
[∵ 1000 meter = 1 km. Thus, 1 meter = 1 /1000 km]
= 2 /10 km
Thus, distance = 0.2 km
And, given time = 10 second
= 10 /60 × 60 hour
= 1 /360 hour
Thus, time = 1 /360 hour
Calculation of speed in km/h using formula
Now we know that,
Speed = Distance/Time
Thus, the speed of the given athlete in km/h
= 0.2 km /1/360hour
= 0.2 × 360 km/h
= 72 km/h
Thus, speed of the given athlete = 72 km/h Answer
[After observing the result obtained here, it is better to calculate the speed in m/s using the given units and after that change the speed from m/s to the required km/h.
The using of type of method depends upon the situation. ]
Calculation of speed using Unitary Method when time and distance are given]
Given, Distance = 200 meter
And, Time = 10 second
∵ In 10 second, the distance covered = 200 m
∴ In 1 second, the distance covered = 200 m /10 second
= 20 m/s or 20 meter per second
Conversion from m/s to km/h
Multiply the m/s by 18/5 to convert it into km/h
Here, speed = 20 m/s
Thus, 20 m/s = 20 × 18/5 km/h
= 4 × 18 km/h
⇒ Speed in km/h = 72 km/h
Thus, speed of the given athlete = 72 km/h Answer
Similar Questions
(1) By running at a speed of 17 km/h how much distance a bus will cover in 9 second?
(2) At a certain speed a cyclist covers a distance of 70 km in 3 hours. How much distance will it cover in 4 hour?
(3) Find the distance covered by an athlete in 25 hours if it covers a distance of 72 km in 15 hours.
(4) Find the distance covered by a cricket ball in 27 hours if it covers a distance of 74 km in 17 hours.
(5) By running at a speed of 10 km/h how much distance a scooty will cover in 7 second?
(6) Find the distance covered by a bus in 24 hours if it covers a distance of 52 km in 14 hours.
(7) By running at a speed of 31 km/h how much distance an athlete will cover in 10 second?
(8) By running at a speed of 7 km/h how much distance a bus will cover in 9 second?
(9) By running at a speed of 21 km/h how much distance a scooty will cover in 7 second?
(10) By running at a speed of 12 km/h how much distance a car will cover in 5 second?