Answer:

Explanation:
Momentum is a vector quantity that represents the "amount of motion" of an object.
Mathematically, the momentum of an object is given by

where
m is the mass of the object
v is the velocity
Since momentum is a vector, it also has a direction, which is the same as the velocity.
Therefore, if we have two objects, the total momentum of the two objects will be obtained from the vector sum of the individual momenta of the two objects.
In this problem we have:
is the momentum of object A
is the momentum of object B
Therefore, the total momentum of objects A and B can be obtained by adding each components of A to the corresponding component of B, so:

So the total initial momentum is

Answer:
All the observers are correct.
Explanation:
This is simply a problem of reference frames from which the motion of the book is being viewed by the various observers.
From their various reference frames, they are all correct.
Observer A must be in the inertial reference frame.
<em>Observers who can explain the behavior of the book and the car by using the relationship between the sum of the forces and changing velocity are said to be observers in inertial reference frames.</em>
This is clearly shown by what observer A noticed. There was a relative motion between the book and the car as she pointed out, making her to be in an inertial reference frame.
<em>Similarly, observers in inertial reference frames can also explain the changes in velocity of objects by considering the forces exerted on them by other objects.</em>
This is shown by observer B as he is able to notice how the force of the car affects the velocity of the book.
Observer C is actually in a non-inertial reference frame, as newtons law of force motion relationship are no longer observed. This occurs in the non inertial reference frame.
Answer: mammals may be relatively better at solving problems than birds.
As the water russhes toward the shore, it rises because it is pushing against it.<span />