Step-by-step explanation:
v=70km/h
t=7 seconds
u=0
first change the unit km/h to m/s
1000km=1m
3600seconds=1h
v=70km/h ×1000km/3600s
v=19.44m/s
acceleration =final velocity(v)-initial velocity(u)/time
acceleration=19.44m/s-0m/s=19.44m/s
19.44/7=2.78 m/s