Question

7.

A car having an initial velocity of 12 meters per second

west slows uniformly to 2. 0 meters per second west in

4. 0 seconds. The acceleration of the car during this 4. 0

second time interval is

(1) 2. 5 m/s west

(2) 6. 0 m/s west

(3) 2. 5 m/s² east

(4) 6. 0 m/s east

Proof. Show calculation.

Answer 1

(3) 2.5 m/s² east

Step-by-step explanation:

a = (vf - vi)/t

vf = 2 m/s

vi = 12 m/s

t = 4 s

a = (2 m/s - 12 m/2) / 4 s = -10 m/s / 4 s = - 2.5 m/s²

The negative sign means the car is slowing down (negative acceleration).

The car is going west and slows down, so the direction of the acceleration vector will be opposite to the direction of its initial motion, which is to the west. Therefore, the direction of the acceleration vector would be east.