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Question
Joseph jogs from one end A to the other end B of a straight 300 m road in 2 minutes 30 seconds and then turns around and jogs 100 m back to point C in another 1 minute. What are Joseph’s average speeds and velocities in jogging?
- from A to B and
- from A to C?
Solution
(a) From A to B.
Time for A to B = 2 min 30s
= 2 × 60 + 30
= 150 s
`"Average speed" = "total distance"/ "time interval"`
= `300/150`
= 2 ms-1
`"Average velocity" = "displacement"/ "time interval"`
= `300/150`
= 2 ms-1
(b) From A to C.
Time taken = A to B + B to C
= 150 + 60
= 210 s
Total distance = 300 + 100
= 400 m
∴ `"Average speed" = "total distace"/"time interval"`
= `400/210 `
= 1.9 m s-1
∴ `"Average velocity" = "displacement"/"time interval"`
= `200/210`
= 0.95 ms-1
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