To calculate the average acceleration, we can use the formula:
\[ a = \frac{v_f - v_i}{t} \]
where:
- \( a \) is the average acceleration,
- \( v_f \) is the final velocity,
- \( v_i \) is the initial velocity,
- \( t \) is the time period over which the change occurs.
Given:
- \( v_f = 45 \) m/s (final velocity),
- \( v_i = 55 \) m/s (initial velocity),
- \( t = 5.0 \) s (time).
Now, we can substitute these values into the equation:
\[ a = \frac{45 , \text{m/s} - 55 , \text{m/s}}{5.0 , \text{s}} = \frac{-10 , \text{m/s}}{5.0 , \text{s}} = -2 , \text{m/s}^2 \]
The average acceleration of the boat is \(-2 , \text{m/s}^2\). This negative sign indicates that the boat is decelerating.