I need help with an ACCELERATION word problem. Thank you.?

Question

1. A jumbo jet is taxiing down the runway but is told to return to the the gate to pick up a very important passenger. The jet is traveling at 45.0 m/s when the pilot receives the message, and it takes 5.00 s to bring the plane to a stop in order to turn around.

1. What is the acceleration of the plane?

2. Vivian is walking to the hair salon at pace of 1.3 m/s when she realizes she could be late. She gradually quickens her pace at 0.090 m/s^2.

2. After 10.0 seconds, how fast is she moving?

Thank you.

Answer 1

1. Since the plane is slowing down from 45 m/s to 0m/s (to stop), the acceleration is actually negative i.e., deceleration.

Acceleration = (Final velocity - Initial velocity) / time = (0 - 45) / 5

                   = -9 m/s^2

2. Vivian's initial velocity = 1.3 m/s. Acceleration is 0.09 m/s^2

    Final velocity = Initial Velocity + (Acceleration * time)

    V at 10 s = 1.3 + (0.09*10) = 1.3 + 0.9 = 2.2 m/s

You may want to read up on basic laws of kinematics. Good luck!

Answer 2

1.) The final velocity is 0 m/s because it has to come to a stop:

0 = 45 + a(5)

-45 = 5a

a = -9 m/s^2

2.) v = 1.3 + 10(.09)

v = 2.2 m/s

Just use this formula (only for constant acceleration):

Final velocity = initial velocity + (acceleration x time)

vf = vi + at