- Define and explain Types of Forces in your own words
- Use key terms such as weight accurately
- Apply what you have learned to new examples and questions
- Avoid the common mistakes learners make with this topic
This lesson focuses on Types of Forces: meeting contact forces like friction and non-contact forces like gravity and magnetism.
Meeting contact forces like friction and non-contact forces like gravity and magnetism.
Key ideas
Forces are pushes, pulls and twists
Forces act between objects and are measured in newtons. Contact forces need touching — friction, tension and the normal push of a surface. Non-contact forces act at a distance — gravity, magnetism and static electricity. Drawing them as arrows shows both size and direction at a glance.
Balanced forces mean no change in motion
When forces are equal and opposite they cancel, giving a resultant force of zero. A book resting on a table and a car cruising at steady speed both have balanced forces. Unbalanced forces leave a non-zero resultant, which accelerates the object in that direction — this is the heart of Newton's second law.
Key term — weight: The force of gravity pulling on an object's mass, measured in newtons, with W = m × g.
Is magnetism a contact or non-contact force?
Non-contact — a magnet pulls iron without touching it.
Answer: Non-contact — a magnet pulls iron without touching it.
- Saying balanced forces mean the object is stationary Balanced forces also allow steady-speed motion — a car at a constant speed has balanced forces.
- Thinking friction is always a nuisance Friction lets tyres grip roads and brakes stop cars — engineers only reduce it where it is unhelpful.
Practice
0 N — the forces are balanced, so the rope does not accelerate.
The forces are balanced — air resistance upwards equals weight downwards, so the resultant force is zero.
Mass stays the same; weight drops to about one-sixth because the Moon's gravity is weaker.
Uphill, a component of the car's weight pulls it backwards down the slope, so the engine must supply extra force to balance it and keep the resultant at zero.
Quick check
Which of these best defines "weight"?
A 5 kg bag has what weight on Earth? (g = 10 N/kg)
- Types of Forces: meeting contact forces like friction and non-contact forces like gravity and magnetism.
- Forces are pushes, pulls and twists: Forces act between objects and are measured in newtons.
- resultant force: The single force that has the same effect as all the forces acting on an object combined.
- Watch out for: saying balanced forces mean the object is stationary