Answer:
m = 9795.9 kg
Explanation:
v = 35 m/s
KE = 6,000,000 J
Plug those values into the following equation:

6,000,000 J = (1/2)(35^2)m
---> m = 9795.9 kg
I believe it’s A. I know for sure it isn’t D.
Answer:
45 m / s North is a valid vector reading for an object.
Explanation:
Then velocity will be defined by x km / hr North. And, magnitude of velocity defines the speed of the body. Although this tells the speed, but there is no description for the direction, so it's not a vector reading
By looking at the acceleration of the object.
In fact, Netwon's second law states that the resultant of the forces acting on an object is equal to the product between the mass m of the object and its acceleration:

So, when static friction is acting on the object, if the object is still not moving we know that all the forces are balanced: in fact, since the object is stationary, its acceleration is zero, and so the resultant of the forces (left term in the formula) must be zero as well (i.e. the forces are balanced).