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Secondary V • 2yr.

How do you distinguish different types of forces (I am in the ATS program)?

Physics

Explanations (1)

• Explanation from Alloprof

Explanation from Alloprof

This Explanation was submitted by a member of the Alloprof team.

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Team Alloprof • 2yr.

Different types of forces are distinguished according to the bodies between which they take place:

• Gravitational force is a force of attraction between two objects. It is this force that holds the Earth and all that covers it together. It is also this force that allows the stars to orbit around each other. We speak of gravitational force especially when it comes to attraction between different bodies (which do not necessarily produce an electromagnetic field).

• A normal force is a force that exists when one object presses on another. For example, standing on the ground (thanks to gravity) generates a normal force. The ground reacts against the gravitational force, thus allowing a person to remain stationary. We speak of a normal force when another force pushes on an object, and that the latter remains stationary, or its speed is constant. In short, a normal force cannot exist on its own.

• Friction is a force that operates between two objects that rub against each other. For example, the brakes on a bicycle act in opposition to the rotating wheels, slowing the vehicle. Like normal forces, friction doesn’t exist on its own. It exists in reaction to another force, which causes it.

• Electromagnetic force is a force of attraction or repulsion that operates only between bodies with an electric charge or magnetic poles. Care must be taken to distinguish it from gravitational force, since both can cause attraction. However, only electromagnetic force can cause repulsion.

• Strong and weak nuclear forces only apply to subatomic particles on a very small scale. The strong nuclear force holds protons and neutrons together, while the weak nuclear force is related to radioactivity.

We also sometimes speak of other "types" of force, which in reality are terms regrouping different categories of forces:

• Resultant force: when several forces are applied to a body, the different forces are added and sometimes cancel. This ensures that the result of the addition of the forces can be regarded as a new force, that is, the resultant force.

• Balancing force: to keep a body in place, it is necessary to cancel the sum of the forces acting on it (therefore, the resulting force). The balancing force is that force which cancels out the resulting force.

• Effective force: this is the component of a force responsible for moving an object. In other words, it is the “useful” part of that force, regardless of whether the “unnecessary” parts of the force have been canceled out or not. Care must be taken to distinguish it from the resultant force.

Do not hesitate if you have other questions!