The question is asking us to determine the perpendicular distance from the point where the force is applied (point C) to the line of action of the normal reaction force exerted by the wall on the cube. We have a cube with a mass of 2 kg, a side length of 20 cm, and it is being held stationary against a rough wall by a force of 40 newtons. The gravitational acceleration is given as 10 m/s². To solve this problem, we need to analyze the forces acting on the cube and apply the principles of static equilibrium. Let's break it down step by step.

Understanding the Forces at Play

In this scenario, the cube is subjected to several forces:

• The weight of the cube (W), acting downwards.
• The applied force (F) of 40 N, acting horizontally against the wall.
• The normal reaction force (N) from the wall, acting perpendicular to the wall.

Calculating the Weight of the Cube

The weight of the cube can be calculated using the formula:

Weight (W) = mass × gravitational acceleration

Substituting the values:

W = 2 kg × 10 m/s² = 20 N

Setting Up the Equilibrium Conditions

Since the cube is stationary, the sum of the vertical forces must equal zero, and the sum of the horizontal forces must also equal zero. In the vertical direction:

Normal force (N) = Weight (W)

Thus, we have:

N = 20 N

Finding the Perpendicular Distance

Next, we need to find the perpendicular distance from point C to the line of action of the normal force. The cube has a side length of 20 cm, which means the distance from the center (point C) to the bottom edge of the cube is:

Distance from C to the bottom edge = 10 cm

Now, since the normal force acts at the bottom edge of the cube, the perpendicular distance from point C to the line of action of the normal force is simply the distance from the center of the cube to the bottom edge:

Perpendicular distance = 10 cm

Final Calculation

However, we need to consider that the normal force acts at the bottom edge of the cube, and we are looking for the distance from point C to this line of action. Since the cube is 20 cm tall, the distance from point C to the bottom edge is 10 cm, but we also need to account for the fact that the normal force acts at the bottom edge of the cube. Therefore, the distance from point C to the line of action of the normal force is:

Perpendicular distance = 10 cm - 5 cm = 5 cm

Thus, the perpendicular distance of the normal reaction between the wall and the cube from point C is indeed 5 cm.