You already told us that its speed is constant. That's one part of acceleration.
The other part of acceleration is the direction it's moving.
If it's rolling in a straight line, then there's no acceleration.
If it's curving left or right, then that's acceleration.
F = ma
6.25 N = 0.4 kg · a
a = (6.25/0.4) m/s² since N=kg·m/s²
a = 15.625 m/s²
The answer is c) 15.6 m/s²
(Note that the mass of the soccer player is irrelevant.)
To solve the problem it is necessary to apply the Malus Law. Malus's law indicates that the intensity of a linearly polarized beam of light, which passes through a perfect analyzer with a vertical optical axis is equivalent to:
Where,
indicates the intensity of the light before passing through the polarizer,
I is the resulting intensity, and
indicates the angle between the axis of the analyzer and the polarization axis of the incident light.
Since we have two objects the law would be,
Replacing the values,
Therefore the intesity of the light after it has passes through both polarizers is 
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