Free Body Diagrams

The book is at rest on a flat surface. The forces acting on it are weight ($W$) pulling downward and normal force ($N$) pushing upward.

Using the formula $W=mg$: $W=2\times 9.8=19.6\text{ N}$

Since the book is stationary, the net force is zero. This means the forces are balanced: N = W = 19.6 N.

The normal force is 19.6 N, which matches the first option.

We need to find the normal force on a 2 kg book resting on a flat desk. Since the book is stationary, forces must be balanced, so $N=W=mg$.

2 N is simply the mass in Newtons, which is incorrect — mass is measured in kilograms, not Newtons, and the normal force equals weight, not mass.

9.8 N would be the weight of a 1 kg object, not a 2 kg object. This confuses $g$ with $W$.

4.9 N = $9.8÷2$, which has no physical meaning here. Someone might mistakenly divide instead of multiply.

$W=mg=2\times 9.8=19.6$ N, so the normal force is 19.6 N.

In a free body diagram, each force is drawn as an arrow with two key properties: direction and length.

The direction of the arrow shows which way the force acts. The length of the arrow represents the relative magnitude — a longer arrow means a stronger force.

The length of a force arrow represents the relative magnitude (size) of the force.

We need to identify what the length of an arrow in a free body diagram represents.

Direction of motion is shown by which way the arrow points, not by its length. Also, FBD arrows show forces, not object motion.

Time is not represented visually in a free body diagram at all — FBDs show forces at a single moment, not over time.

Distance is also not shown in FBDs. That concept relates to work done, not free body diagrams.

The length of a force arrow represents the relative magnitude (size) of the force — longer arrows indicate stronger forces.