Normal Force Solved Examples: A Comprehensive Guide

📚 Quick Study Guide

• ⬆️ Normal force ($F_N$) is the force exerted by a surface on an object in contact with it. It acts perpendicular to the surface.
• 📐 Normal force is a reaction force, meaning it arises in response to an applied force.
• ⚖️ On a horizontal surface, if the only vertical force is gravity, then $F_N = mg$, where $m$ is mass and $g$ is the acceleration due to gravity ($9.8 m/s^2$).
• наклоне On an inclined plane, $F_N = mg \cos(\theta)$, where $\theta$ is the angle of inclination.
• 💡 Normal force is crucial in calculating frictional force, as $F_f = \mu F_N$, where $\mu$ is the coefficient of friction.
• 📝 Remember to always draw a free body diagram to visualize all forces acting on the object.

🧪 Practice Quiz

1. A 5 kg box is resting on a horizontal surface. What is the normal force acting on the box?

   1. 49 N
   2. 5 N
   3. 0 N
   4. 9.8 N

2. A book is placed on a table. Which of the following statements is true about the normal force?

   1. It acts parallel to the table surface.
   2. It is equal to the weight of the book if the table is horizontal.
   3. It is zero if the book is not moving.
   4. It always opposes the force of friction.

3. A 10 kg block is resting on an inclined plane at an angle of 30 degrees with the horizontal. What is the normal force acting on the block?

   1. 98 N
   2. 84.9 N
   3. 49 N
   4. 0 N

4. What happens to the normal force if you push down on a box resting on a horizontal surface?

   1. It decreases.
   2. It increases.
   3. It remains the same.
   4. It becomes zero.

5. A 2 kg block is sliding down an inclined plane with an angle of 45 degrees. Assuming there is friction, what is the relationship between the normal force and the weight component perpendicular to the plane?

   1. Normal force is greater than the weight component.
   2. Normal force is less than the weight component.
   3. Normal force is equal to the weight component.
   4. Normal force is zero.

6. A person is standing in an elevator. When the elevator accelerates upwards, what happens to the normal force acting on the person?

   1. It decreases.
   2. It increases.
   3. It remains the same.
   4. It becomes zero.

7. A box is being pushed against a wall. The applied force is horizontal. What provides the normal force in this scenario?

   1. Gravity
   2. The applied force
   3. Friction
   4. The weight of the box