Explanation:
Make a table, listing the x and y coordinates of each square's center of gravity and its mass.  Multiply the coordinates by the mass, add the results for each x and y, then divide by the total mass.

The x-coordinate of the center of gravity is 15/14 a.
The y-coordinate of the center of gravity is 47/42 a.
 
        
             
        
        
        
Answer:
Work done, W = 750 joules
Explanation:
It is given that,
Force acting on the object, F = 50 N
It moves to a distance of, d = 15 meters
We need to find the work done on an object. We know that the product of force and distance covered is called the work done. As the force and the displacement are in same direction. So, 


W = 750 joules
So, the work done on an object is 750 joules. Hence, this is the required solution.
 
        
             
        
        
        
The work required to stop the car is equal to the amount of kinetic energy that the car currently has. This is given by E=(1/2)mv^2. Since the energy is proportional to the square of the velocity, that factor will have the greatest influence on the work required to stop it.