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Question:

Physics question (8 grade)?

A subway excavator lifts a person standing on it in 1 minute.The person climbs op on the unmoving/not working excavator in 3 minutes.In what time will the person climb on the working/moving excavator?(This is translated from another language)

Answer:

A subway excavator lifts a person standing on it in 1 minute.The person climbs op on the unmoving/not working excavator in 3 minutes.In what time will the person climb on the working/moving excavator? This is a relative speed problem. d = distance that they move upward. The speed of the excavator = d ÷ 60 seconds. The speed of the person = d ÷ 180 seconds The sum of speeds = d/60 + d/180 = 3 d/ 180 + d/180 = 4d/180 = d/45 Time = distance ÷ speed = d ÷ d/45 = 45 seconds = 0.75 minute This makes sense, because the time should be less than the other 2.

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