To find the acceleration of the car, we can use the formula for acceleration, which is given by:
\[ a = \frac{{v_f - v_i}}{{t}} \]
where:
- \( a \) is the acceleration,
- \( v_f \) is the final velocity,
- \( v_i \) is the initial velocity, and
- \( t \) is the time interval.
Given:
- Initial velocity (\( v_i \)) = 16.0 m/s (east)
- Final velocity (\( v_f \)) = 6.0 m/s (east)
- Time interval (\( t \)) = 4.0 s
Now we can plug in the values:
\[ a = \frac{{6.0 , \text{m/s} - 16.0 , \text{m/s}}}{{4.0 , \text{s}}} \]
Calculating the numerator:
\[ 6.0 , \text{m/s} - 16.0 , \text{m/s} = -10.0 , \text{m/s} \]
Now, substituting back into the formula:
\[ a = \frac{{-10.0 , \text{m/s}}}{{4.0 , \text{s}}} = -2.5 , \text{m/s}^2 \]
Thus, the acceleration of the car during the 4.0-second interval is:
\[ \boxed{-2.5 , \text{m/s}^2} \]
This negative value indicates that the car is decelerating (slowing down) in the eastward direction.