Hello, I need help understanding where to start as in figuring out how to start

Question

Hello, I need help understanding where to start as in figuring out how to start these problems.

A driver, starting from rest, accelerates at a rate of 2 m/s2 for 15 s unil reaaching a certain speed. She then continues driving at this constant speed for an additional 15 s.

a) What is the maximum speed reached by the driver?

b) What total distance does the dirver cover during the 30s that she is in motion?

c) What is the driver's average speed during the first 15 s that she's in motion?

d) What is the driver's average speed during the full 30 s that she is in motion?

At t= 30s, the driver brakes hard, coming to a stop over a distance of 20 m.

e) how much time does it take the driver to come to a stop?

f) What is the driver's accerleration during this braking?

Thanks in advance for any help and explanation, it's greatly appreciated!

e)

Explanation / Answer

Part A)

Apply vf = vo + at

vf = 0 + 2(15)

vf = 30 m/s

Part B)

During the acceleration

d = vot + .5at2

d = 0 + .5(2)(15)2 = 225 m

During the constant speed

d = vt = 30(15) = 450 m

Total distance = 450 + 225 = 675 m

Part C)

Average speed = d/t

d/t = 225/15

Average speed is 15 m/s

Part D)

Average Speed = 675/30 = 22.5 m/s

Part E)

Apply vf2 = vo2 + 2ad

0 = 302 + 2(a)(20)

a = -22.5 m/s2 (This is the answer to part F and needed for part E)

Then apply

vf = vo + at

0 = 30 + (-22.5)(t)

t = 1.33 sec

Part F)

See above

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