The situation given in option A and B are examples for moving an object toward left side while the option C and option D are examples for moving an object toward right side. Option B will also be an example for not moving the object.
Explanation:
As per the option A statement, the force acting towards left is greater than the force acting toward right side. So the net force will be towards the direction having maximum magnitude. Thus, the box will move toward left side in option A. The same situation arises for the object in option B. But here the difference in the forces is only 1 N, so the change in the position of the object will be very less. Thus it may look like there is no acceleration in the box of option B.
Similarly, the force acting on the objects given in option C and D have magnitude greater towards the right side than towards the left side. So these two will be accelerated toward the right side.
Not totally sure but i would say a normal? its not refraction or incidence if its perpendicular and i dont think its a mirror if its an imaginary line so yeah normal (normals are always perpendicular to their surface too i think so)
The kinetic energy of a book on a shelf is equal to the work done to lift the book to the shelf is false. The kinetic energy on the shelf is zero because it is not in action.
