9. A force is applied horizontally to a 20 kg box on a flat table, if the acceleration of the box is 2 m/s and the coefficient of friction between the box and the table is 0.5, what was the magnitude (number) of the
applied force?

By Newton's second law,

n + (-w) = 0

p + (-f ) = (20 kg) (2 m/s²)

where n is the magnitude of the normal force, w is the weight of the box, p is the magnitude of the applied force (p for push or pull), and f is the magnitude of the friction force.

Calculate the weight of the box:

w = (20 kg) (9.80 m/s²) = 196 N

Then

n = w = 196 N

and

f = µ n = 0.5 (196 N) = 98 N

Now solve for p :

p - 98 N = 40 N

p = 138 N

the working equation for the angular size is the product of the physical size and 360 degrees divided by the product of two pi and distance from earth. the minimum size would be 0.559 degrees while the maximum size would be 0.49 degrees. 

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