Answer:
9 seconds
Explanation:
[tex]acceleration = \frac{final \: speed - initial \: speed}{time \: taken} [/tex]
[tex]5km/ hr/ s = \frac{45 - 0 (km/ h)}{t} [/tex]
cross multiplying
[tex]5t = 45 secs \\ t = 9 \: secs[/tex]
it will take 9secs for the car to go from 0 to 45 km/ h
