Contact Forces (HL IB Physics)

• A contact force is defined as:

A force which acts between objects that are physically touching

• Examples of contact forces include:
  • Friction
  • Air resistance
  • Tension
  • Normal (reaction) force

Friction

• Friction is a force that opposes motion
• Occurs when objects rub against each other e.g. car wheels on the ground

Air resistance

• Air resistance is a type of friction
• Occurs when an object moves through air e.g. an object in freefall

Tension

• Tension is a force that pulls two objects connected by a length of something, such as a string or rope
• Occurs when a force is applied to the length e.g. a spring extending

Normal / reaction force

• Reaction forces occur when an object is supported by a surface
• It is the component of the contact force acting perpendicular to the surface that counteracts the body e.g. a book on a table

Examples of contact forces