Answer:
4 x 10⁶m/s²
Step-by-step explanation:
Given parameters: 
Initial velocity = 0m/s 
Time = 0.0001s 
Final velocity = 400m/s 
Unknown: 
Acceleration of the object = ? 
Solution: 
Acceleration is the rate of change of velocity with time; 
 Acceleration = 
 
 
 Acceleration = 
 = 4 x 10⁶m/s²
 = 4 x 10⁶m/s²