To find the acceleration of the car, we can use the formula:

$a = \frac{{\Delta v}}{{\Delta t}}$

where:

• $\Delta v$ is the change in velocity,
• $\Delta t$ is the time interval.

Given:

• Initial velocity $v_i = 20 \, \text{m/s}$,
• Final velocity $v_f = 45 \, \text{m/s}$,
• Time interval $\Delta t = 5 \, \text{seconds}$.

Now, let's calculate the change in velocity $\Delta v$: $\Delta v = v_f - v_i = 45 \, \text{m/s} - 20 \, \text{m/s} = 25 \, \text{m/s}.$

Next, we calculate the acceleration: $a = \frac{{\Delta v}}{{\Delta t}} = \frac{{25 \, \text{m/s}}}{{5 \, \text{s}}} = 5 \, \text{m/s}^2.$

Therefore, the acceleration is:

$\boxed{5 \, \text{m/s}^2}.$

The correct answer is C. 5 m/s².

Would you like further details on how this is calculated or on acceleration in general?

Here are 5 related questions for practice:

1. What is the final velocity of a car that starts at 10 m/s and accelerates at 4 m/s² for 6 seconds?
2. If a car decelerates at 3 m/s² and comes to a stop from 30 m/s, how long does it take?
3. How far does a car travel if it accelerates from 0 to 20 m/s in 4 seconds?
4. What is the change in velocity of a truck that accelerates at 6 m/s² for 10 seconds?
5. If a car takes 8 seconds to go from 5 m/s to 25 m/s, what is its acceleration?

Tip: Acceleration is a vector quantity, meaning it has both magnitude and direction.