Normal Force: Mass on a Surface

In summary, when a mass is on a surface, it applies a force to it due to its weight. According to Newton's 3rd law, the surface also applies a force to the mass. This force is commonly referred to as the normal force. In general, the normal force is the projection of the reaction force onto the surface normal. In the case of a horizontal surface, the normal force is equal to the reaction force. However, if the surface is tilted, the normal force will be smaller than the reaction force due to the projection. For more information, diagrams can be found on the Wikipedia page for normal force.
  • #1
ShayanJ
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When a mass is on a surface,It applies a force to it because of its weight.According Newton's 3rd law,the surface applies a force to the mass.Can we call this force,Normal force?
 
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  • #2
In general you would have that the normal force is the projection of the reaction force onto the surface normal.

In your example, if the surface is horizontal, then the reaction force (the force Newtons 3rd law say is opposite the weight in a static situation) is already normal to the surface, so the normal force is in this case the same as the reaction force. If the surface was tilting (but still flat, to keep it simple), then the projection of the reaction force onto the surface normal would give a normal force of smaller magnitude than the reaction force.

See http://en.wikipedia.org/wiki/Normal_force for a few diagrams.
 

FAQ: Normal Force: Mass on a Surface

What is the normal force?

The normal force is the force exerted by a surface on an object in contact with it, perpendicular to the surface. It is called the "normal" force because it is always perpendicular to the surface, or "normal" to it.

What causes the normal force?

The normal force is caused by the repulsive forces between the atoms or molecules of the surface and the object in contact with it. These forces are known as the electrostatic forces.

How is the normal force related to mass?

The normal force is not directly related to the mass of the object. It is dependent on the weight of the object, which is equal to its mass multiplied by the acceleration due to gravity. Therefore, the normal force increases as the weight of the object increases.

Does the normal force always have the same magnitude?

No, the magnitude of the normal force can vary depending on the weight of the object and the angle at which it is placed on the surface. For example, if the object is on an inclined plane, the normal force will be less than the weight of the object.

How does the normal force affect the motion of an object?

The normal force is a reactionary force that helps to balance out other forces acting on an object. It is essential in keeping objects stable and preventing them from sinking into a surface. In terms of motion, the normal force does not directly influence the acceleration of an object, but it plays a crucial role in maintaining equilibrium and preventing the object from falling through the surface.

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