Answer:
 45 s .
Explanation:
The accelerator will first accelerate , then move with uniform velocity and at last it will decelerate to rest . 
displacement s = ?
acceleration a = 1 m /s²
Final speed v = 5 m/s 
initial speed u = 0 
v² = u² + 2as 
5² = 0 + 2 x 1 x s 
s = 12.5  m 
B)  Let time of acceleration or deceleration be t 
v = u + a t 
5 = 0 + 1 t 
t = 5 s 
Similarly displacement during deceleration = 12.5 m 
Total distance during uniform motion = 200 - ( 12.5 + 12.5 ) =  175 m .
velocity of uniform motion = 5 m /s 
time during which there was uniform velocity = 175 / 5 = 35 s 
Total time = 5 + 35 + 5 = 45 s . 
 
        
             
        
        
        
Explanation:
Th electric force between charges is inversely proportional to the square of distance between them. It means,

Initial distance, r₁ = 2 cm
Final distance, r₂ = 0.25 cm
Initial force, F₁ = 1 N     
We need to find the electric force between charges if the new separation of 0.25 cm. So,

So, the new force is 64 N if the separation between charges is 64 N.
 
        
             
        
        
        
The earth is so round that we can run around it in five million days