Sunlight and gravity are not considered matter because sunlight does not have a rest mass that is characteristic of matter while gravity is just a vector component of matter.
<u>Explanation:</u>
Sunlight has energy and momentum that makes it similar to matter but it cannot be considered matter when you consider all the factors that are characteristic of matter. Light is an electromagnetic wave that is made up of photons and the protons do not have rest mass.
Gravity is a vector component of matter that has both magnitude as well as direction and the gravity increases with increase in mass of an object.
Given :
Initial speed of car A is 15 m/s and initial speed of car B is zero.
Final speed of car A is zero and final speed of car B is 10 m/s.
To Find :
What fraction of the initial kinetic energy is lost in the collision.
Solution :
Initial kinetic energy is :

Final kinetic energy is :

Now, fraction of initial kinetic energy loss is :

Therefore, fraction of initial kinetic energy loss in the collision is 1.25 .
The strength of the force of friction depends on two factors; the type of surfaces involves and the force that the surfaces are being push together
F=W=mg
12N(given)= m*9.8
m= 1.22 kg