It can be described as a constant variation
        
             
        
        
        
Answer:
Explanation:
Applied force, F = 18 N
Coefficient of static friction, μs = 0.4
Coefficient of kinetic friction, μs = 0.3
θ = 27°
Let N be the normal reaction of the wall acting on the block and m be the mass of block. 
Resolve the components of force F. 
As the block is in the horizontal equilibrium, so 
F Cos 27° = N 
N = 18 Cos 27° = 16.04 N
As the block does not slide so it means that the syatic friction force acting on the block balances the downwards forces acting on the block .
The force of static friction is μs x N = 0.4 x 16.04 = 6.42 N   .... (1)
The vertically downward force acting on the block is mg - F Sin 27° 
                                                       = mg - 18 Sin 27° = mg - 8.172    ... (2)
Now by equating the forces from equation (1) and (2), we get 
mg - 8.172 = 6.42 
mg = 14.592 
m x 9.8 = 14.592
m = 1.49 kg
Thus, the mass of block is 1.5 kg.  
 
        
             
        
        
        
Answer:
The answer is
<h2>4 hrs</h2>
Explanation:
To find the time taken we use the formula

where
d is the distance covered
v is the velocity
t is the time
From the question
d = 1200 miles
v = 300 mi/hr
We have

We have the final answer as
<h3>4 hrs</h3>
Hope this helps you