The magnitude of the acceleration of the car is given by:
[tex]a= \frac{v_f-v_i}{t} [/tex]
where
[tex]v_i=15 m/s[/tex] is the initial speed of the car
[tex]v_f=25 m/s[/tex] is the final speed of the car
[tex]t=4.0 s[/tex] is the time it takes for the car to change its speed
Substituting these data into the formula, we find the magnitude of the average acceleration of the car:
[tex]a= \frac{25 m/s-15 m/s}{4.0 s}=2.5 m/s^2 [/tex]
therefore, the correct answer is (1) 2.5 m/s^2.
