4.5.1.4 Forces

Spec reference: 4.5.1 (subtopic).

What you need to know

• forces acting. Some energy is lost into the environment.
• Lubricants, such as oil, can be used to reduce the friction between the
• surfaces.
• Conduction – when a solid is heated, the particles vibrate and collide
• more, and the energy is transferred.
• Convection – when a liquid or a gas is heated, the particles move faster.
• This means the liquid or gas becomes less dense. The denser region will
• rise above the cooler region. This is a convection current.

Self-assessment (checklist)

• I can explain what is meant by a resultant force.
• I can calculate the resultant of two forces that act in a

Key steps (method)

• Identify what the question is testing and use the correct equation/definition.
• Show substitutions and units clearly.

Common mistakes

• Unit conversions, rearranging errors, or quoting a law without applying it.