Average acceleration = (change in speed) / (time for the change)
= (70 km/hour) / (7 seconds)
= 10 km/hr-sec .
That's a valid unit of acceleration ... [ length / time² ] ...
but it's so clunky that we can't relate to it. We usually
want to see acceleration in m/s² . So I'll convert this
answer to the more conventional unit.
(10 km/hr-sec) · (1,000 m / 1 km) · (1 hr / 3,600 sec)
= (10 · 1,000 · 1) / (1 · 3,600) m/s²
= 2.78 m/s² ( about 0.28 G )