Three sprinters A, B, and C had to sprint from points P to Q, which are 55 meters apart, and back again (starting in that order). The time interval between their starting times was 5 seconds each. C started 10 seconds after A, while B started 5 seconds after A. They passed a certain point R, which is somewhere between P and Q, simultaneously (none of them having reached point Q yet). Having reached Q and reversed the direction, the third sprinter met the second one 9m short of Q and met the first sprinter 15m short of Q.
Find the speed of the three sprinters.
(In reply to
soln by Steven Lord)
I agree that the problem is ill-defined in the way Steven defines. I have a question about the speed ratios proposed in Steven's solution, however.
Since (eq 1) and (eq 2) equate times, shouldn't (eq 1) be
70/SC-10 = 40/SA ? 70/SC = 40/SA implies that same starting time of C and A, which is not true. C has a speed of zero for 10 seconds, then a speed of SC. Without the "-10" in the equation, SC will be 10 seconds late getting to the 70/40 meeting point.
Same issue for (eq 2)?
Given the above, I believe the correct ratios of the speeds are
SA=.374SC
SB=.816SC
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Posted by Kenny M
on 2019-09-27 13:18:04 |
re: soln
