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 
Answer:
6.86 N
Explanation:
Applying,
F = mg............... Equation 1
Where F = Force exerted by gravity on the mass, m = mass, g = acceleration due to gravity
Note: The Force exerted by gravity on the mass is thesame as the weight of the body.
From the question,
Given: m = 700 g = (700/1000) = 0.7 kg
Constant: g = 9.8 m/s²
Substitute these values into equation 1
F = 9.8(0.7)
F = 6.86 N
1) 15 / 12 = 1.25 ratio
2) to increase acceleration 1.25 times (with same F, or same engine) you have to lower mass 1.25 times
3) 1515/1.25 = 1212 kg
choose A
