Non-Contact Forces
Non-Contact Forces
- A non-contact force is defined as:
A force which acts at a distance, without any contact between bodies, due to the action of a field
- Examples of non-contact forces include:
- Gravitational force, Fg
- Electrostatic force, Fe
- Magnetic force, Fm
- Gravitational force:
- The attractive force experienced by two objects with mass in a gravitational field e.g the force between a planet and a comet
- Electrostatic force:
- A force experienced by charged objects in an electric field which can be attractive or repulsive e.g. the attraction between a proton and an electron
- Magnetic force:
- A force experienced between magnetic poles in a magnetic field that can be attractive or repulsive e.g. the attraction between the north and south poles of magnets
Examples of non-contact forces
Worked example
Ben drags a sledge behind him as he climbs up a hill.
Describe the contact and non-contact forces involved in this scenario.
Answer:
Step 1: Identify the contact forces
- Ben pulls on a rope attached to the sledge producing tension in the rope
- The ground supports Ben and the sledge with a reaction force
- There is friction between the sledge and the ground which opposes the motion
- There is also friction between Ben’s shoes and the ground allowing Ben to climb the hill without slipping down
- A very small force due to air resistance slows Ben’s motion up the hill
Step 2: Identify the non-contact forces
- The gravitational attraction between the Earth and Ben pulls Ben and the sledge downwards
