Normal Force

In physics, numerous kinds of forces exist, one of which is the normal force. The normal force is defined as the force that a surface employs on any other body. If that body is at rest, it means that the net force acting on the body is equal to zero. This means that the downward force, that is, the weight, must be similar to the upward force, which is the normal force.

Concept of Normal Force

The normal force is a force that is felt every day. For example, when we place a book on a table, the typical reaction force resists the book from falling through the table, the strength of gravity is drawing the book downward, but the book isn’t falling. That means, there exists some force which must be pushing it up. That force is termed the normal force. The word ‘normal’ here means perpendicular to the surface.

One more example of normal force can be seen while bouncing a ball: as the normal force is a non-conservative force, it is also related to the friction force; both these forces are non-conservative forces.

If a ball is dropped from a certain height, it falls; gravity pulls the ball down, so it speeds up, while the drag from air slows down the fall. A massive normal force pushes the ball upwards when it hits the ground, which makes the ball bounce not as high as it bounced at the start. The normal force can also be perceived as non-conservative in the case of rolling resistance.

Normal Force Formula

Formula 1: When the force is acting on a body, dropping at an angle of θ, then the F_N is larger than the articulated weight,

F_N = F sin θ + mg

Where,

θ = the angle with which the body falls

F_N = normal force

m represents the mass of the body

and g represents the force of gravity

Formula 2: When a body is pulled upwards by force, then F_N is smaller than its weight

F_N = mg – F sin θ

Where,

θ = angle with which body moves up

F_N = normal force

m = the mass of the body

g = the force of gravity

Formula 3: When a body is resting on the flat surface, the normal force F_N is

F_N = mg

Where,

g = the force of gravity

m = mass

Formula 4: When the body is positioned on an inclined level, then normal force F_N is given by

F_N = mg cos θ

Where,

θ = the angle of the inclined surface

F_N = normal force

m = mass of the body

g = the force of gravity

Watch the video to learn more about force and its types

Relation between Friction Force and Normal Force

When you try to move an object, then the force of Friction, F_friction, acts opposite to the force you apply.

According to the laws of physics, friction is proportional to the force with which you are trying to slide the object on a surface.

You can see in the figure the force with which the gold bar presses against the ground is just its weight or mg.

Then in accordance with Newton’s third law of motion, the ground presses the bar back.

The force perpendicular to the surface pushing the gold bar is called the normal force, denoted by N.

In other words, the force pushing the two surfaces together is the normal force, and the stronger the normal force, the stronger the force due to Friction.

Both these forces, the normal force and the friction force are perpendicular components of the equal force—the force that a surface employs on an object! – The normal and friction forces increase proportionally; if the force exerted by the surface on an object increases.

Read More: Friction

Normal Force Examples

As per the definition and points mentioned above, you must have understood the exact meaning of force. Now, Let’s know more by Some real-life examples of normal force –

1. A Girl standing on a flat surface

The girl in the above picture is standing perpendicular on the flat surface; hence, a perpendicular force acts on the girl. This force will now be termed a Normal Force as it is acting perpendicularly to the girl.

2. Television resting on a table

When a television rests on a table, a perpendicular force exists on television. As this force is acting perpendicularly to the surface of television, this force will be none other than a Normal Force.

Conclusion: From the above examples, it is clear that when a force acts in a perpendicular direction, it will be termed a Normal Force.

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