A car, moving along a straight stretch of highway,

begins to accelerate at 0.0499 m/s

2

. It

takes the car 71.2 s to cover 1 km.

How fast was the car going when it first

began to accelerate?

Answer in units of m/s.

We know that an object in moving with acceleration follow the rule according that the distance covered will be : d = Vi*t + 1/2*a*t^2 where d is distance, Vi is initial speed, and a is acceleration Then after 1 km which is 1000 metres we have: 1000 = Vi * 71.2 + 1/2*0.0499 * (71.2) ^2 Vi = (1000-1/2*0.0499 * (71.2) ^2) / 71.2 = 1000/71.2 - 1/2*0.0499*71.2 = 12.27 m/s Then the car was going at 12.27 m/s when started to accelerate.