Answer:
A. Geocentric: This model is Earth Centered
. Retrograde motion is explained by epicycles
.
B. Heliocentric: This model is Sun centered.  Retrograde motion is explained by the orbital speeds of planets
C. Both geocentric and heliocentric: Epicycles and deferents help explain planetary motion
. Planets move in circular orbits and with uniform motion
. The brightness of a planet increases when the planet is closest to Earth.
Explanation:
The principle of the Ptolemy's geocentric model was developed on the assumption that the center of the universe is the Earth. On the other hand, the principle of the Copernicus' heliocentric model was based on the assumption that the center of the universe is the sun. However, both models have a common ideology on uniform circular motion and epicycles.
 
        
             
        
        
        
Answer:
The minimum compression is  
Explanation:
From the question we are told that 
               The mass of the block is 
                The spring constant is  
                The coefficient of static friction is  
For the the block not slip it mean the sum of forces acting on the  horizontal axis is equal to the forces acting on the vertical axis 
      Now the force acting on the vertical axis is the force due to gravity which is mathematically given as 
                    
And the force acting on the horizontal axis is  force due to the spring which is mathematically represented as 
                    
where x is the minimum compression to keep the block from slipping 
         Now equating this two formulas and making x the subject 
                       
substituting values we have 
                      
                         
 
  
 
        
             
        
        
        
Answer: The pressure that one experiences on the Mount Everest will be different from the one, in a classroom. It is because pressure and height are inversely proportional to each other. This means that as we move up, the height keeps on increasing but the pressure will keep on decreasing. This is the case that will be observed when one stands on the Mount Everest as the pressure is comparatively much lower there.
It is because as we move up, the amount of air molecules keeps on decreasing but all of the air molecules are concentrated on the lower part of the atmosphere or on the earth's surface.
Thus a person in a low altitude inside a classroom will experience high pressure and a person standing on the Mount Everest will experience low pressure.
 
        
             
        
        
        
Answer:
The true course:  north of east
 north of east
The ground speed of the plane: 96.68 m/s
Explanation:
Given:
 = velocity of wind = = velocity of wind = 
 = velocity of plane in still air = = velocity of plane in still air = 
Assume:
 = resultant velocity of the plane = resultant velocity of the plane
 = direction of the plane with the east = direction of the plane with the east
Since the resultant is the vector addition of all the vectors. So, the resultant velocity of the plane will be the vector sum of the wind velocity and the plane velocity in still air.

Let us find the direction of this resultant velocity with respect to east direction:

This means the the true course of the plane is in the direction of  north of east.
 north of east.
The ground speed will be the magnitude of the resultant velocity of the plane.

Hence, the ground speed of the plane is 96.68 km/h.
 
        
             
        
        
        
It will  be stand 46.67 all i did was divide both numbers but im not sure if im right but i hope i am hope i helped:)