1.4 Non-contact forces - examples of forces between objects not touching each other

If the objects are subjected to a force, but do not need to be in contact with each other, the force would be described as a non-contact force e.g. three classic non-contact force fields acting between objects that are not touching ...

Gravity

The gravitational field attraction force between any two objects.

Any object in a gravitational field experiences the force of gravity.

note:

(i) A falling object in air, experiences the non-contact force of gravity and the contact force of friction between the object and air - air resistance.

(ii) Objects in contact with each other will still experience the 'non-contact' force of gravitational attraction - any object standing motionless on a surface.

 

Magnetism

The magnetic force field of attraction between a magnetised material and another magnetic material - which may or may not be already magnetised.

Any object that is magnetic or can be magnetised, will experience a force from the magnetic field of a magnet.

This can be the magnetic force of attraction of iron towards a magnet (permanent and induced N-S pole attraction), two magnets attracted by their opposite poles (N-S <= N-S), or two like poles of magnets repelling each other (N<=>N or S<=>S poles) - possible magnetic field effects.

You see the magnetic field non-contact force in action as a magnet attracts and picks up an iron nail. Initially there is no contact, but once attached there is contact, but the attractive force is still present even if they are in contact.

You can have an object is suspended by magnetic repulsion, where there is no contact at all.

 

Electrostatic force

The attraction (+ -) or repulsion (- - or + +) interaction of two objects carrying an electrical charge - the attractive electrical field force effect.

A simple example is a rubbed charged plastic rod picking up tiny bits of paper.

See Static electricity and electric fields, uses and dangers of static electricity

Note: gravity only involves attraction (as far as we know?), but magnetic and electrical forces involve both the forces of attraction and repulsion.

Using SEARCH some initial results may be ad links you can ignore - look for docbrown

INDEX of my physics notes on FORCES Section 1. An introduction