Answer:
Mary's average speed is 0.42 meters/second.
Explanation:
Mary's total travel was 250 meters and the elapsed time was 10 minutes, equivalent to 600 seconds.
d = displacement = 80 meters + 125 meters + 45 meters = 250 meters
t = time = 10 minutes . 60 seconds/minute = 600 seconds
We can obtain now the average speed:
s = average speed = displacement / time = 250 meters / 600 seconds ≅ 0.4167 ≅ 0.42
Magnitude of acceleration = (change in speed) / (time for the change) .
Change in speed = (ending speed) - (starting speed)
= zero - (43 m/s)
= -43 m/s .
Magnitude of acceleration = (-43 m/sec) / (0.28 sec)
= (-43 / 0.28) (m/sec) / sec
= 153.57... m/s²
= 1.5... x 10² m/s² .