Answer:
t = 4 seconds
Step-by-step explanation:
Given that,
Initial speed, u = 28 m/s
Final speed, v = 42 m/s
Acceleration, a = 3.5 m/s²
We need to find time taken by the car. So, using the first equation of motion as follows :
v=u+at

So, he will need 4 seconds to accomplish this.