Physics
posted by y912f on .
1.what is the shortest possible time in which a bacterium could travel a distance of 8.4 cm across a Petri dish at a constant speed of 3.5 mm/s.
the answer is 24s. how?
3.An athlete swims from the north end to the south end of a 50.0m pool in 20.0s and makes the return trip to the starting position in 22.0s.
a. What is the average velocity for the first half of the swim?
the answer is 2.50m/s to South
b. What is the average velocity for the second half of the swim?
the answer is 2.27m/s to North
c. What is the average velocity for the roundtrip?
the anser is 0.0 m/s
i have the answers, i need to know how to GET to the answers..step by step please.

can anyone answer these two questions??

convert cm to mm
8.4 cm times 10mm per cm equals 84mm
84mm divided by 3.5mm per s equals 24s
calculate average velocity for the first half of trip
50.0m divided by 20.0 equals 2.5m per s
calculate average velocity for 2nd half of trip
50.0 m divided by 22.0 s equals 2.27 m per s
average velocity is
change in distance divided by change in time
50m minus 50m divided by 22.0 s minus 20.0 s equals 0 m per s
I'm not certain about this one. But, I hope it helps. 
24s