Question

At the end of a race, a runner decelerates from a velocity of 9.00 m/s at a rate of 2.00 m/s2 .

(a) How far does she travel in the next 5.00 s?
(b) What is her final velocity?
(c) Evaluate the result. Does it make sense?

Answer 1

20m; -1m/s; doesn't make sense.

Step-by-step explanation:

(a) v=u-at

v=9-2×5

v=-1 m/s

Now, v²=u²-2as

(-1)²=(9)²-2×2×s

4s=81-1=80

s=80/4=20m

(b) v=u-at

v=9-2×5

v=-1 m/s

(c) A runner starts the race at a velocity of 9 m/s and then decelerates at a rate of 2m/s² and her final velocity is -1m/s. This doesn't make sense because that negative final velocity means the runner is running backwards.