A boy is running on a straight road. He runs 500 m towards north in 2 minutes 10 seconds and then turns back and runs 200 m in 1 minute. Calculate i) His average speed and magnitude of average velocity during first 2 minutes 10 seconds and ii) His average speed and magnitude of average velocity during the whole journey.
A boy is running on a straight road. He runs 500 m towards north in 2 minutes 10 seconds and then turns back and runs 200 m in 1 minute. Calculate
i) His average speed and magnitude of average velocity during first 2 minutes 10 seconds and
ii) His average speed and magnitude of average velocity during the whole journey.
Solution:
Given:
- Distance covered towards north = 500 m
- Time taken = 2 minutes 10 seconds = 130 s
- Then he runs back 200 m in 1 minute = 60 s
(i) First 2 minutes 10 seconds
This is only the first part of the motion.
Distance covered = 500 m
Time taken = 130 s
(a) Average Speed :-
Average Speed = Total Distance / Total Time = 500 / 130 = 3.85 m/s
(b) Magnitude of Average Velocity :-
Displacement = 500 m towards north
Average velocity = Displacement / Time = 500 / 130 = 3.85 m/s
(ii) Whole journey
Total distance covered = 500 + 200 = 700 m
Total time taken = 130 + 60 = 190 s
(a) Average speed :-
Average speed = 700 / 190 = 3.68 m/s
Displacement for whole journey
He goes 500 m north , then comes back 200 m
Net displacement = 500 - 200 = 300 m (north)
(b) Magnitude of Average velocity :-
Average velocity = 300 / 190 = 1.58 m/s
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