1) Size of the image: 2 cm
In order to calculate the size of the image, we can use the following proportion:

where
p = 80 m is the distance of the tree from the pinhole
q = 20 cm = 0.2 m is the distance of the image from the pinhole
 = 8 m is the heigth of the object
 = 8 m is the heigth of the object
 is the height of the image
 is the height of the image
By re-arranging the proportion, we find

2) Magnification: 0.0025
The magnification of a camera is given by the ratio between the size of the image and the size of the real object:

so, in this problem we have

 
        
             
        
        
        
The electrostatic force between two charges is inversely 
proportional to the square of the distance between them.
So if you want to multiply the force by, say, ' Q ', 
you need to multiply the distance by  ( 1 / √Q ) .
We want to multiply the force by 16, so we need to
multiply the distance by    ( 1 / √16 )  =  ( 1 / 4 ) .
The distance should be changed to  1/4  of what it is now.
        
                    
             
        
        
        
Answer:
10N
Explanation:
Equation: ΣF = ma
Fapp = ma
Fapp = (2kg)(5m/s^2)    (im guessing you mean 5.00 m/s^2 not m/s)
Fapp = 10*kg*m/s^2
Fapp = 10N
 
        
             
        
        
        
Answer:
Without it, we could not survive on Earth. Earth orbits the sun due to the gravity of the sun, which maintains us at a convenient distance from it to enjoy the sun's warmth and light. It keeps the air we need to breathe and our atmosphere in place. Our planet is held together by gravity.