Answer:

the answer is A.
Explanation:
Using the laws of newton:
∑F = ma
where ∑F is the sumatory of forces acting in the system, m the mass and a the acelertion of the system. 
Then, if the block is moving with constant velocity, its aceleration is equal to 0, so:
∑F = m(0)
∑F = 0
It means that:
F - = 0
 = 0
where F is the force applied and  is the friction force. Replacing the value of F, we get:
 is the friction force. Replacing the value of F, we get:
310N - = 0
 = 0
Finally, solving for  :
:

 
        
             
        
        
        
A billiard ball. unless hit, the balls stay at rest. however when hit into another, the balls do not stop unless acted upon by another force.
        
                    
             
        
        
        
Answer:
191433.4 hours 
Explanation:
We are given that In the average US household, the television is on 6.75 hours/day! How many hours will have passed after 77.7 years (the average lifeexpectancy of an American)?
1 year - 365 days
Given that the television is on 6.75 hours/day.
If 1 year = 365 days 
Convert 77.7 years to days by multiplying it by 365
77.7 × 365 = 28360.5 days
So the number of hours will be:
28360.5 × 6.75 = 191433.375 hours 
Therefore, 191433.4 hours will pass.
Non of the options is correct. 
 
        
             
        
        
        
Answer:
Explanation:
Polyatomic ions are ions that contain more than one atom in each one of the ions.   
Ionic compounds are made of cations (positive ions) and anions (negative ion). By convention, the cation is written before the anion.
List the ions in each compound:
<h3>CaCO₃</h3>
Cation:  ,
,
Anion:  .
.
 is a monatomic ion for it contains only one atom in each ion.
 is a monatomic ion for it contains only one atom in each ion. 
 is a polyatomic ion for it contains four atoms (one C atom and three O atoms) in each ion.
 is a polyatomic ion for it contains four atoms (one C atom and three O atoms) in each ion.
<h3>NaF</h3>
Cation:  ,
,
Anion:  .
.
Both  and
 and  are monatomic for they contain only one atom in each ion.
 are monatomic for they contain only one atom in each ion. 
<h3>FeO</h3>
Cation:  ,
,
Anion:  .
.
Both  and
 and  are monatomic for they contain only one atom in each ion.
 are monatomic for they contain only one atom in each ion. 
<h3>CaCl₂</h3>
Cation:  ,
,
Anion:  .
.
Both  and
 and  are monatomic for they contain only one atom in each ion.
 are monatomic for they contain only one atom in each ion. 
<h3>NaOH</h3>
Cation:  ,
,
Anion:  .
.
 is a monatomic ion for it contains only one atom in each ion.
 is a monatomic ion for it contains only one atom in each ion. 
 is a polyatomic ion for it contains two atoms (one O atom and one H atom) in each ion.
 is a polyatomic ion for it contains two atoms (one O atom and one H atom) in each ion.
 
        
                    
             
        
        
        
Answer:
B ) Ascend using my buddy alternative air source / make an emergency Ascent
Explanation:
From the description it can be seen his buddy is close by of which he can easily use the alternative air source. Also we can see that he is closer to the water surface than his buddy, of which controlled emergency swimming ascent is highly favourable in this condition.