a car accelerates along a straight road from the rest to 90 km/h in 5 s what is the magnitude of its average acceleration

2 answers

5sec = 5/3600 hours

change in velicity is 90 km/h in 5/3600 hrs so the acceleration is

90km/h/(5/3600 hr) = 90*3600/5 km/hr^2 = 64800 km/hr^2

Not the units you wanted? Well, I'll let you change from km/hr^2 to m/s^2
Jean baptiste