6.
The S.I. unit of speed is-
km/minute
m/minute
km/hour
✓ m
m/second
D. Answer the following questions in brief.
1. A boy walks to his school with a constant speed of 4 km/h and reaches there in
30 minutes. Find the distance of the school from his house.
2
The distance between two stations is 216 km. A bus takes 4 hours to cover this
distance. Calculate the average speed of the bus in km/hour
3.
Two Cars, A and B, (starting at the same time, from the same point) are moving
with average speeds of 40 km/h and 50 km/h, respectively, in the same direction
Find how far will Car B be from Car A after 3 hours.
4. A car moves with a speed of 40 km/h for 15 minutes and then with a speed of
60 km/h for the next 15 minutes. Find the total distance covered by the car in
these 30 minutes,
5. Define the term 'Periodic motion. Give two examples of periodic motions that
can be used to measure time.
Answers
Answer:
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Explanation:
1. A boy walks to his school with a constant speed of 4 km/hour and reaches there in 30 minutes. Find the distance of the school from his house.
Solution- Given- speed = 4 km/ h
Solution- Given- speed = 4 km/ hTime = 30 min= 30 / 60 = ½ h
Solution- Given- speed = 4 km/ hTime = 30 min= 30 / 60 = ½ hDistance = speed x time = 4 km/h x ½h = 2 km
Solution- Given- speed = 4 km/ hTime = 30 min= 30 / 60 = ½ hDistance = speed x time = 4 km/h x ½h = 2 kmAns- distance of the school from his house is 2 km.
2. The distance between two stations is 216 kilometre. A Bus takes 4 hours to cover this distance. Calculate the average speed of the bus in km per hour.
Solution- Given- Distance = 216 km
Solution- Given- Distance = 216 kmTime = 4 hours
Solution- Given- Distance = 216 kmTime = 4 hoursAverage speed = total distance covered / time taken
Solution- Given- Distance = 216 kmTime = 4 hoursAverage speed = total distance covered / time taken= 216 km/ 4 h
Solution- Given- Distance = 216 kmTime = 4 hoursAverage speed = total distance covered / time taken= 216 km/ 4 h=54 km /h
Solution- Given- Distance = 216 kmTime = 4 hoursAverage speed = total distance covered / time taken= 216 km/ 4 h=54 km /hAns- average speed of the bus = 54 km/h
3.Two cars A and B starting at the same time from the same point are moving with average speed of 40 kilometre per hour and 50 km per hour respectively in the same direction. Find how far will car B be from car A after 3 hours.
Solution- Given- Average speed of car A = 40 km/h
Average speed of car B =50 km/h
Time = 3 hours
Distance covered by car A = speed x time = 40 x 3 = 120 km
Distance covered by car B = speed x time = 50 x 3 = 150 km
Distance between car A and car B after 3 hours =150 km - 120 km = 30 km
Ans - Car B will be 30 km ahead of car A after 3 hours
4. A car moves with a speed of 40 km per hour for 15 minutes and then with a speed of 60 km per hour for the next 15 minutes. Find the total distance covered by the car in these 30 minutes.
Ans- CASE 1:
Ans- CASE 1:speed of car = 40 km/h, time = 15 min = 15/60 hour = ¼ hour
Ans- CASE 1:speed of car = 40 km/h, time = 15 min = 15/60 hour = ¼ hourDistance covered in this 15 min = speed x time = 40 x ¼ = 10 km
Ans- CASE 1:speed of car = 40 km/h, time = 15 min = 15/60 hour = ¼ hourDistance covered in this 15 min = speed x time = 40 x ¼ = 10 kmCASE 2 :
Ans- CASE 1:speed of car = 40 km/h, time = 15 min = 15/60 hour = ¼ hourDistance covered in this 15 min = speed x time = 40 x ¼ = 10 kmCASE 2 :Speed of car = 60 km/h , time = 15 min = 15/ 60 hour = ¼ hour
Ans- CASE 1:speed of car = 40 km/h, time = 15 min = 15/60 hour = ¼ hourDistance covered in this 15 min = speed x time = 40 x ¼ = 10 kmCASE 2 :Speed of car = 60 km/h , time = 15 min = 15/ 60 hour = ¼ hourDistance covered in next 15 min = speed x time = 60 x ¼ = 15 km
Ans- CASE 1:speed of car = 40 km/h, time = 15 min = 15/60 hour = ¼ hourDistance covered in this 15 min = speed x time = 40 x ¼ = 10 kmCASE 2 :Speed of car = 60 km/h , time = 15 min = 15/ 60 hour = ¼ hourDistance covered in next 15 min = speed x time = 60 x ¼ = 15 kmTotal distance covered in 30 min= 10 + 15 = 25 km
5. Define the term periodic motion. Give two examples of periodic motions that can be used to measure time.
Ans. The motion which repeats itself after regular intervals of time is called periodic
Ans. The motion which repeats itself after regular intervals of time is called periodic motion.
Ans. The motion which repeats itself after regular intervals of time is called periodic motion.Examples of periodic motions that can be used to measure time are -
Ans. The motion which repeats itself after regular intervals of time is called periodic motion.Examples of periodic motions that can be used to measure time are -(i)the rotation of the earth about its axis (which takes twenty hours)
Ans. The motion which repeats itself after regular intervals of time is called periodic motion.Examples of periodic motions that can be used to measure time are -(i)the rotation of the earth about its axis (which takes twenty hours)(ii)the revolution of the earth around the sun (which takes 365 days.)