AQA A Level Physics

Revision Notes

7.1.1 Force Fields

Concept of a Force Field

  • A force field is any region of space where a body will experience a non-contact force
    • This will cause the body to move, interact or be deformed in some way
  • A non-contact force is a force that acts without physical contact
    • Pushing a trolley is a contact force
    • A fridge magnet being attracted to the metal on a fridge is a non-contact force
  • Force fields arise from the interactions between bodies or particles
    • Static or moving charged particles experience a force in an electric field
    • Moving charged particles experience a force in a magnetic field
    • Particles with mass experience a force in a gravitational field
  • For example, the effects of the Moon and Sun’s gravitational fields can be seen on Earth, such as the cause of tides

Contact and Non-contact Forces, downloadable AS & A Level Physics revision notes

Examples of contact and non-contact forces

Direction of a Force Field

  • The direction of a force field can be represented as a vector, the direction of which must be determined by inspection
  • The direction of the vector shows the direction of the force that would be exerted on that body if it was placed in that position in the field
  • The direction of a force field is shown by field lines (or ‘lines of force’), which are represented by arrows
  • A force field on a three-dimensional object is the force acting over the whole three-dimensional object
    • For spherical objects, such as a planet, the object can be approximated to a point mass

Direction of a Force Field, downloadable AS & A Level Physics revision notes

The direction of the gravitational force is shown by the vector field lines

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