AQA A Level Physics复习笔记7.1.1 Force Fields

• 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

Examples of contact and non-contact forces

• 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

   

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