A reference point would be something not on the ship which could be used to calculate distance traveled.
Answer: C.) A lighthouse on a nearby Island
 
        
                    
             
        
        
        
Concrete is not a polymer which Nylon, and Kevlar are
        
                    
             
        
        
        
The net force = sum of all forces acting on the body
If we take left side as -ve and right side as +ve,
then,
The net force here would be equal to,
10N + (- 3N)
= 7N.
Therefore, a net force of +7N ( + indicates it's moving towards right) is acting on the book of mass 2kg.
        
             
        
        
        
Answer:
 a = 1 m/s²  and 
Explanation:
The first two parts can be seen in attachment
We use Newton's second law on each axis
Y axis
       Ty - W = 0         
       Ty = w
X axis
      Tx = m a
With trigonometry we find the components of tension
     Sin θ = Ty / T
     Ty = T sin θ
     Cos θ = Tx / T
     Tx = T cos θ
We calculate the acceleration with kinematics
    Vf = Vo + a t
    a = (Vf -Vo) / t
    a = (20 -10) / 10
    a = 1 m/s²
We substitute in Newton's equations
      
   T Sin θ = mg
   T cos θ = ma
We divide the two equations
   Tan θ = g / a
   θ = tan⁻¹ (g / a)
   θ = tan⁻¹ (9.8 / 1)
   θ = 84º
We see that in the expression of the angle the mass does not appear therefore you should not change the angle